Question

•The Internal Revenue Service (IRS) claims that its forms should typically take about 160 minutes to fill out.

•A researcher believes that the IRS's claim is not correct and that it generally takes people longer to complete each of the forms.

•She recorded the time (in minutes) it took 20 individuals to complete each form.

•Do you agree with the IRS’ claim, or do you think that the researcher is correct?

278

71

201

101

83

133

110

119

180

26

239

302

110

152

62

21

237

268

121

129

You should perform a relevant test to see if the central value of the time to fill it is 160.

•Check the normality of the sample to determine which test is appropriate.

•Construct confidence intervals for the mean/median for each group.

•Use plots, e.g. boxplots/histograms to illustrate your data, and describe how they relate to your results.

Answer 1

The probability plot is:

This sample is normally distributed.

The hypothesis being tested is:

H0: µ = 160

Ha: µ ≠ 160

The p-value is 0.4970.

Since the p-value (0.4970) is greater than the significance level (0.05), we fail to reject the null hypothesis.

Therefore, we can conclude that forms should typically take about 160 minutes to fill out.

The 95% confidence interval for the mean is between 108.308 and 185.992.

160.000	hypothesized value
147.150	mean Data
82.993	std. dev.
18.558	std. error
20	n
19	df
-0.692	t
.4970	p-value (two-tailed)
108.308	confidence interval 95.% lower
185.992	confidence interval 95.% upper
38.842	margin of error