Question

Four different paints are advertised to have the same drying times. To verify themanufacturer’s claim, seven samples were tested for each of the paints. The time in minutes until the paint was dry enough for a second coat to be applied was recorded. Below are the results which may be imported into MSExcel for analysis: (Assume the populations are normally distributed, the populations are independent and the population variances are equal)

Paint 1 120 112 121 118 118 121 118

Paint 2 120 130 121 126 126 114 117

Paint 3 117 122 123 115 123 126 126

Paint 4 128 131 131 129 127 126 137

1. Write the Null and Alternative hypothesis to test whether there is a difference in dry time between the samples of each paint?

2. What statistic would you use to analyze this?

3. At a 0.01 level of significance, what would be your decision rule?

4. From your analysis, is there a difference between drying times?

5. If there was a difference in dry times how would you determine which paint has the different drying time? (i.e. what formula would you use and what is your decision criteria?) (this is not asking for a calculation)

Answer 1

From the given data

Thus we conclude that there is significance difference among the 4 population means

From the given data

The mean of paint 4 is more than remaining means of three paints