Question

Surveys were sent to a random sample of owners of all-wheel-drive (AWD) vehicles and to a random sample of owners of front-wheel-drive (FWD) vehicles. The proportion of owners who were satisfied with their vehicles was recorded for each sample. The sample proportions were used to construct the 95 percent confidence interval for a difference in population proportions (FWD minus AWD) for satisfied owners. The interval is given as (−0.01,0.12). A car company believes that the proportion of satisfied owners of AWD vehicles differs from the proportion of satisfied owners of FWD vehicles. Does the confidence interval provide evidence that this belief is plausible?

Answer 1

No, the confidence interval does not provide evidence that this belief is plausible as the confidence interval range contains the null value (0)

Explanation:

Given that the confidence interval for the mean difference of AWD and FWD vehicles is :

(−0.01,0.12)

When defining the hypothesis for mean difference :

H0 : μ1 - μ2 = 0

H1 : μ1 - μ2 ≠ 0

Using the confidence interval result, reject the Null if the confidence interval value at the given α - level does not contain 0 ; otherwise fail to reject the Null ;

Since the (−0.01,0.12) contains 0 ; then we fail to reject the Null and conclude that there is no statistically significant difference between the two groups