sabunabu
Please see the below and my answers-- please let me know if you disagree and also if you know the answers to the 2 questions I don't. Any help is greatly appreciated.
PoolVac, Inc. manufactures and sells a single product called the âSting Ray,â which is a patent-protected automatic cleaning device for swimming pools. PoolVacâs Sting Ray accounts for 65 percent of total industry sales of automatic pool cleaners. Its closest competitor, Howard Industries, has captured 18 percent of the market.
Using the last 26 months of its sales data, PoolVac wishes to estimate demand for its Sting Ray. Demand for Sting Rays is specified to be a linear function of its price (P), average income for households that have swimming pools in the U.S (MAVG) and the price of the competing pool cleaner sold by Howard Industries (PH). The general linear form of the demand function
Qd = a + b P + c MAVG + d PH.
The attached computer printout presents the regression output from 26 observations (monthly data) on the price charged for a Sting Ray (P), average income of households with pools (MAVG), and the price Howard industries charged for its pool cleaner (PH).
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The printout of part of regression output from Minitab for the empirical demand is below:
Regression Analysis: Q versus P, MAVG, PH
Predictor Coef SE Coef T P
Constant 2728.8 531.7 5.13 0.000
P -10.758 1.330 -8.09 0.000
MAVG 0.021420 0.009452 2.27 0.034
PH 3.166 1.344 2.36 0.028
S = 73.0546 R-Sq = 96.6% R-Sq(adj) = 96.2%
Analysis of Variance
Source DF SS MS F P
Regression 3 3379846 1126615 211.10 0.000
Residual Error 22 117414 5337
Total 25 3497260
Source DF Seq SS
P 1 3327368
MAVG 1 22878
PH 1 29600
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1. An estimated demand equation for PoolVac is:
Qd = 2728.8-10.758P+0.021420M+3.166Ph
2. Evaluate the statistical significance of the three estimated slope parameters using a significance level of .05 or 5 percent (you can either use p-values or do a t-test).Please, explain how you decided each parameter was statistically significant or not.
Since the P values of all 3 variables are within the 5% confidence interval, each variable should be considered as staristically significant in determining the demand of the pool vacuums.
3. What is the exact level of statistical significance for estimated slope parameters on price, average income of household and price of related good? Please, explain how you know.
We should look at the P value for each of the slope parameters and in doing so, we find that price is 100% significant, average income (Mavg) is 96.6% (100-.034) and price of competition (Ph) is 97.2% significant (100-.028).
4. Discuss the appropriateness and/or interpretations of the algebraic signs of the three slope parameters, based on your theoretical expectations. Interpret the numerical values of the three slope parameters in the context of this regression.
5. Now evaluate the overall fit of the estimated (sample) regression equation to the data.
a. What percentage of variability in Qd (linear) is explained by a model? Does it indicate a good overall fit? Please, explain.
b. Verify whether the overall regression equation is statistically significant, another words, verify the goodness of overall fit .What is the exact level of significance for the entire regression equation?
Looking at the F stat which is 211.1, we can say the overall regression equation is significant since the absolute value is large. Also, the P value is 0 so there is no chance that this regression equation doesnât explain the relationship between the given variables and quantity demanded.
Answer
All of your answers are good. To say that the F statistic has a large absolute value is a little vague; one would generally either consult an F table to the appropriate threshold value or just look at the P value in the computer output. On the other hand, it isn't wrong, and if your instructor taught it that way you should leave it in.
Regarding the questions you haven't answered, number 4 refers to the direction of the effects on your dependent variable that come with changes in the independent variables. You should look at your coefficients and consider what would happen if you changed the values in your variables. For example, if the price of the product goes up, demand for the product goes down because of the negative coefficient associated with the price variable. If this seems confusing, try plugging in some different values into the equation and calculating the result. The negative coefficient makes sense, because people are going to be less interested in buying something if its more expensive. The question is asking you to evaluate both the actual effects on demand and the expected effects for each of the variables.
Question 5a refers to the R-squared statistic (R-Sq), which is the percent of explained variability as mentioned in the question. Yours is quite high.
All of your answers are good. To say that the F statistic has a large absolute value is a little vague; one would generally either consult an F table to the appropriate threshold value or just look at the P value in the computer output. On the other hand, it isn't wrong, and if your instructor taught it that way you should leave it in.
Regarding the questions you haven't answered, number 4 refers to the direction of the effects on your dependent variable that come with changes in the independent variables. You should look at your coefficients and consider what would happen if you changed the values in your variables. For example, if the price of the product goes up, demand for the product goes down because of the negative coefficient associated with the price variable. If this seems confusing, try plugging in some different values into the equation and calculating the result. The negative coefficient makes sense, because people are going to be less interested in buying something if its more expensive. The question is asking you to evaluate both the actual effects on demand and the expected effects for each of the variables.
Question 5a refers to the R-squared statistic (R-Sq), which is the percent of explained variability as mentioned in the question. Yours is quite high.
How do you get rid of efflorescence on Pavers/Stones?
CuriousJor
My steps were built using Rinox pavers and I've got alot of efflorescence on them. The contractor told me that this was a normal process from the concrete curing process and that it goes away after a short while. It's almost 3 years later and It's still there. Does anyone know if this is going to go away or how to treat it. I find it so unattractive everytime I look at it.
Thanks
Answer
Cleaning and Sealing Paving Stones
STONESAVER® premium concrete surface cleaners, water repellent and sealers have been formulated to provide the best cleaning, preparation and sealing system on the market. Originally developed for the commercial paving surface industry, STONESAVER® products have been put to the test by many satisfied professionals for years before finally being offered to the retail public.
Rust Remover.
Removes stubborn rust stains from paving stones and concrete.
Citrus Oil Degreaser
Uses a unique blend of citrus extracts to removes oil and grease stains from paving stones and concrete.
Stripper
Removes paint, graffiti, rubber, tar and chewing gum from paving stones and concrete.
Cleaner and Surface Prep
Essential pre-sealing surface preparation ensures vibrant colour and proper sealer to surface bonding.
Removes efflorescence, dirt and tire marks from paving stones and concrete.
Complete with E-Z Spray auto mixing hose adaptor.
Paving Stone Sealer
Protects paving stones against salt, oil, rust, acid rain, UV colour fading and pool chemicals.
Premium formulation, high acrylic solids.
Colour enhancing wet look.
Will not peel, wears evenly.
Comes in 3.78L and 18L containersâ 1L covers 30 to 40 square feet.
How Long to Wait Until Sealing
Sealing should be done only after the natural efflorescence process has been given time to take place. Efflorescence, being a whitish powder, is the deposit of small quantities of cement from within the pavers on its top surface after a series of wetting (rainfall) and drying (warm weather) cycles. Because a series of wet/dry cycles are required, which are weather dependant, there is no exact time frame which applies to every situation. However, allowing 8 weeks, with a minimum of 4 precipitation events during that time, is a common rule of thumb.
Stain Removal
Between installation and sealing, some pavers may become stained due to foot and vehicle trafficâ this is common. However, it is important to remove these stains prior to sealing or else their appearance through sealing may become enhanced.
The first step is to inspect for any extremely stained, cracked or broken units which should be replaced. All items which cast shadows on the area (e.g. furniture) should be removed, if possible, to allow the area to dry evenly once stain removal and cleaning is completed. Similarly, automatic sprinkler systems should be turned off during cleaning and sealing operations.
Prior to using any of these products, refer to the respective productsâ
labels for personal protection, installation and first aid suggestions.
Start stain removal at the bottom of the pavement and work up the slope in manageable sections. This prevents untreated areas from becoming wet, which can hide some stains.
Rust Remover- Pre-wet the stained area with water. Apply a liberal amount of the stain remover to the stained area only and let stand for two minutes. Vigorously scrub the stain with a stiff bristle scrub brush and rinse immediately with generous amounts of water. Repeat if necessary.
Citrus Oil Degreaserâ Pre-wet the stained area with water. Apply a liberal amount of stain remover to the stained area and let stand for one minute. Vigorously scrub the stain with a stiff bristle scrub brush and rinse away cleaner and residue thoroughly with water (strong water pressure works best). Stains that have deeply penetrated into the pavers may resurface after initial cleaning and dryingâ repeat stain removal process if necessary.
Stripperâ Remove excess material with a scraper. Apply sufficient Stripper to cover the remaining stain. Allow product to stand for approximately 5 minutes. Do not let product dry on surface. Scrub stained area with a stiff bristle brush. Rinse thoroughly with water (strong water pressure works best). Repeat if necessary.
When all stains are removed, rinse the entire area down to ensure any residuals are washed away.
Cleaning Process
Once the stains are removed, the entire area should be thoroughly cleaned to remove any efflorescence and dirt. Note: Because of the effectiveness of the Surface Cleaner, spot cleaning will be noticeable in the final product; therefore, it is recommended that the entire area be cleaned.
Prior to starting each application, lightly pre-wet the area with water, as well as any vegetated areas that may be subject to overspray and/or runoff. As a precaution, delicate vegetation can be pulled back or covered to protect from overspray.
Concrete Cleaner- Simply attach your water hose to the inlet port of the E-Z sprayer and you are ready to start. Working quickly, start at the lowest point of your surface and work in 27 square metre (300 square feet) pre measured sections. Work side to side, making sure the entire surface is covered. If there is still cleaner remaining in the bottle after the section is done, apply the remaining cleaner as an additional spray over the same areaâ this will reinforce the cleaning application and prevent drying of the surface. Use a long handled stiff bristled broom to brush the treated area, loosening stubborn dirt and deposits. Rinse thoroughly (usually 5-6 rinses with a pressure sprayer until foaming is no longer visible. However, care should be taken to not blow or wash the sand from the jointsâ sand will remain in the joints if a wide spray nozzle is used and the angle of the spray is kept from directly penetrating the joints. Be sure to rinse all cleaner from the surface as you progress to additional sections until the entire surface is cleaned and thoroughly rinsed. Do not let the cleaner dry on surface or stand in low spots as this may stain the pavers; mist surface with water if it begins to dry.
When the entire surface is cleaned and well rinsed, allow to dry and inspect. Repeat application to the white (efflorescence) areas if necessary.
For vegetated areas that were subject to overspray or runoff, dilute the areas one last time with large quantities of clean water.
Sealing
Allow at least 24 hours without moisture or surface dampness before sealing. If the pavers and jointing sand are not totally dry (not just surface dry), moisture blushing may occur under the sealer after it is applied, or the sealer may become cloudy/white.
Never re-sand paving joints between cleaning and sealing applications as this will leave residue on the surface of the pavers.
Paving Stone Sealerâ For best results, use a lint free high pile roller and a metal paint tray, or airless sprayer, to apply the sealer. Apply at a temperature above 7 Degrees C (45 Degrees F). Apply sufficient sealer to fully saturate the surface and penetrate at least 15 mm (5/8â) into the jointing sand. Excess sealer on the surface should be pushed to an unsealed area with a rubber squeegee, which are effective in achieving good penetration but avoid bringing jointing sand to the surface of the pavers.
For surfaces being sealed for the first time, apply a second coat by rolling in a cross direction from the first coat. Allow one hour to dry between applications. Allow sealed surfaces to dry for 24 hours before using.
Cleaning and Sealing Paving Stones
STONESAVER® premium concrete surface cleaners, water repellent and sealers have been formulated to provide the best cleaning, preparation and sealing system on the market. Originally developed for the commercial paving surface industry, STONESAVER® products have been put to the test by many satisfied professionals for years before finally being offered to the retail public.
Rust Remover.
Removes stubborn rust stains from paving stones and concrete.
Citrus Oil Degreaser
Uses a unique blend of citrus extracts to removes oil and grease stains from paving stones and concrete.
Stripper
Removes paint, graffiti, rubber, tar and chewing gum from paving stones and concrete.
Cleaner and Surface Prep
Essential pre-sealing surface preparation ensures vibrant colour and proper sealer to surface bonding.
Removes efflorescence, dirt and tire marks from paving stones and concrete.
Complete with E-Z Spray auto mixing hose adaptor.
Paving Stone Sealer
Protects paving stones against salt, oil, rust, acid rain, UV colour fading and pool chemicals.
Premium formulation, high acrylic solids.
Colour enhancing wet look.
Will not peel, wears evenly.
Comes in 3.78L and 18L containersâ 1L covers 30 to 40 square feet.
How Long to Wait Until Sealing
Sealing should be done only after the natural efflorescence process has been given time to take place. Efflorescence, being a whitish powder, is the deposit of small quantities of cement from within the pavers on its top surface after a series of wetting (rainfall) and drying (warm weather) cycles. Because a series of wet/dry cycles are required, which are weather dependant, there is no exact time frame which applies to every situation. However, allowing 8 weeks, with a minimum of 4 precipitation events during that time, is a common rule of thumb.
Stain Removal
Between installation and sealing, some pavers may become stained due to foot and vehicle trafficâ this is common. However, it is important to remove these stains prior to sealing or else their appearance through sealing may become enhanced.
The first step is to inspect for any extremely stained, cracked or broken units which should be replaced. All items which cast shadows on the area (e.g. furniture) should be removed, if possible, to allow the area to dry evenly once stain removal and cleaning is completed. Similarly, automatic sprinkler systems should be turned off during cleaning and sealing operations.
Prior to using any of these products, refer to the respective productsâ
labels for personal protection, installation and first aid suggestions.
Start stain removal at the bottom of the pavement and work up the slope in manageable sections. This prevents untreated areas from becoming wet, which can hide some stains.
Rust Remover- Pre-wet the stained area with water. Apply a liberal amount of the stain remover to the stained area only and let stand for two minutes. Vigorously scrub the stain with a stiff bristle scrub brush and rinse immediately with generous amounts of water. Repeat if necessary.
Citrus Oil Degreaserâ Pre-wet the stained area with water. Apply a liberal amount of stain remover to the stained area and let stand for one minute. Vigorously scrub the stain with a stiff bristle scrub brush and rinse away cleaner and residue thoroughly with water (strong water pressure works best). Stains that have deeply penetrated into the pavers may resurface after initial cleaning and dryingâ repeat stain removal process if necessary.
Stripperâ Remove excess material with a scraper. Apply sufficient Stripper to cover the remaining stain. Allow product to stand for approximately 5 minutes. Do not let product dry on surface. Scrub stained area with a stiff bristle brush. Rinse thoroughly with water (strong water pressure works best). Repeat if necessary.
When all stains are removed, rinse the entire area down to ensure any residuals are washed away.
Cleaning Process
Once the stains are removed, the entire area should be thoroughly cleaned to remove any efflorescence and dirt. Note: Because of the effectiveness of the Surface Cleaner, spot cleaning will be noticeable in the final product; therefore, it is recommended that the entire area be cleaned.
Prior to starting each application, lightly pre-wet the area with water, as well as any vegetated areas that may be subject to overspray and/or runoff. As a precaution, delicate vegetation can be pulled back or covered to protect from overspray.
Concrete Cleaner- Simply attach your water hose to the inlet port of the E-Z sprayer and you are ready to start. Working quickly, start at the lowest point of your surface and work in 27 square metre (300 square feet) pre measured sections. Work side to side, making sure the entire surface is covered. If there is still cleaner remaining in the bottle after the section is done, apply the remaining cleaner as an additional spray over the same areaâ this will reinforce the cleaning application and prevent drying of the surface. Use a long handled stiff bristled broom to brush the treated area, loosening stubborn dirt and deposits. Rinse thoroughly (usually 5-6 rinses with a pressure sprayer until foaming is no longer visible. However, care should be taken to not blow or wash the sand from the jointsâ sand will remain in the joints if a wide spray nozzle is used and the angle of the spray is kept from directly penetrating the joints. Be sure to rinse all cleaner from the surface as you progress to additional sections until the entire surface is cleaned and thoroughly rinsed. Do not let the cleaner dry on surface or stand in low spots as this may stain the pavers; mist surface with water if it begins to dry.
When the entire surface is cleaned and well rinsed, allow to dry and inspect. Repeat application to the white (efflorescence) areas if necessary.
For vegetated areas that were subject to overspray or runoff, dilute the areas one last time with large quantities of clean water.
Sealing
Allow at least 24 hours without moisture or surface dampness before sealing. If the pavers and jointing sand are not totally dry (not just surface dry), moisture blushing may occur under the sealer after it is applied, or the sealer may become cloudy/white.
Never re-sand paving joints between cleaning and sealing applications as this will leave residue on the surface of the pavers.
Paving Stone Sealerâ For best results, use a lint free high pile roller and a metal paint tray, or airless sprayer, to apply the sealer. Apply at a temperature above 7 Degrees C (45 Degrees F). Apply sufficient sealer to fully saturate the surface and penetrate at least 15 mm (5/8â) into the jointing sand. Excess sealer on the surface should be pushed to an unsealed area with a rubber squeegee, which are effective in achieving good penetration but avoid bringing jointing sand to the surface of the pavers.
For surfaces being sealed for the first time, apply a second coat by rolling in a cross direction from the first coat. Allow one hour to dry between applications. Allow sealed surfaces to dry for 24 hours before using.
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