Question

In an advertisement, a pizza shop claims that the stabdard deviation of deliverh times is les than 3.25 minutes. A random selection of 38 delivery times has a sample mean of 28.5 minutes and a standard deviation of 3.5 minutes. Use a significance level of .01 to test the pizza ship’s claim.

Answer 1

State the claim:-

The pizza shop’s std dev of delivery time is less than 3.25 minutes.

State the Hypotheses:-

Compute the test value:-

To test a claim about the value of the variance or the standard deviation of a population, then the test statistic will follow a chi-square distribution with n?1 dgrees of freedom, and is given by the following formula.

  

  

  

Fnd the P-Value:-

P-value is 0.232 This is calculates in excel by using command as  =CHIDIST(42.911,37)

Decision:-

Since P-value(0.232) > 0.01. We accept  

Final Statement:-

At the 1% level of significance, you have sufficient evidence to conclude that the standard deviation of delivery times is not les than 3.25 minutes.