Question

From her firm's computer telephone log, an executive found that the mean length of 70 telephone calls during July was 4.19 minutes with a standard deviation of 5.46 minutes. She vowed to make an effort to reduce the length of calls. The August phone log showed 50 telephone calls whose mean was 2.134 minutes with a standard deviation of 2.752 minutes.

Steps:

1. Open Minitab on your computer.

2. There is no data file for this example. The information above contains summarized data (take info from story and plug into Minitab)

(a)	Choose the appropriate hypotheses for a right-tailed test to see if calls were quicker, on average, in August. Assume µ1 is the average call length in July and µ2 is the average call length in August.
	a. H0: μ1 – μ2 ≤ 0 vs. H1: μ1 – μ2 > 0
	b. H0: μ1 – μ2 < 0 vs. H1: μ1 – μ2 ≤ 0
	a b

(b-1)

Obtain a test statistic tcalc and p-value assuming unequal variances. (Use Minitab. Round your answers to 3 decimal places.)

tcalc
p-value

(b-2)

Interpret the results using α = .01.

   (Click to select)  Reject  Do not reject  the null hypothesis.

(b-3)

What is your conclusion at α = .01?

  

We   (Click to select)  can  cannot  conclude the length of calls had been reduced

Answer 1

from minitab

a)

a. H₀: μ₁ – μ₂ ≤ 0 vs. H₁: μ₁ – μ₂ > 0

b-1)

t_calc =2.706

p-value =0.004 (for one tailed)

reject  the null hypothesis.

b-3)

can conclude the length of calls had been reduced