Question

The IRS claims that it takes 87 minutes to prepare a tax form. You believe it takes longer than 87 minutes. You ask 19 people and find the following preparation times:

69, 70, 72, 73, 79, 80, 85, 88, 91, 97, 97, 99, 105, 105, 108, 113, 117, 119, 138

Determine if the preparation time is significantly longer than 87 minutes. Use α = .05.

What assumption is necessary to conduct this analysis?

Answer 1

From the given data

= 95 , S = 19.12822

H0: = 87

Ha: > 87

We need to assume that distribution is approximately normally distributed.

Test statistics

t = - / S / sqrt(n)

= 95 - 87 / 19.12822 / sqrt(19)

= 1.82

This is test statistics value.

Critical value at 0.05 level with 18 df = 1.734

Since test statistics falls in rejection region, reject H0.

We conclude at 0.05 level that we have enough evidence to support the claim.