A problem with a telephone line that prevents a customer from receiving or makin
ID: 3157753 • Letter: A
Question
A problem with a telephone line that prevents a customer from receiving or making calls in disconcerting both to the customer and to the telephone company. These problems can be of two types: those that are located inside a central office, and those located on lines between the central office and customer's equipment. The folloing data represent samples of 10 problems reported to two different offices of a telephone company and the time to clear these problems(in minutes) from the customers' lines:
Table: Time to clear problems (minutes)
Central Office I
1.48
1.75
0.78
2.85
0.52
1.60
4.15
3.97
1.48
3.10
Central Office II
7.55
3.75
0.10
1.10
0.60
0.52
3.30
2.10
0.58
4.02
You are given the summarized data:
Central Office I
Central Office II
Sample Mean (X_bar)
2.1680
2.3620
Sample Standard Deviation
1.2735
2.3315
Sample Size
10
10
Pooled Variance
3.5288
Assume that the population variances are equal, you need to find if there is evidence of a difference betweent the two central offices with respect to average time to clear these problems (in minutes) with a significance level of 0.05.
Pooled-variance t test or Separate-variance t test should be used? In your answer, use "P" for Pooled V t test, "S" for Separate t test. Your answer is
The test statistic tstat=
The UPPER critical value tcrit=
Central Office I
1.48
1.75
0.78
2.85
0.52
1.60
4.15
3.97
1.48
3.10
Central Office II
7.55
3.75
0.10
1.10
0.60
0.52
3.30
2.10
0.58
4.02
Explanation / Answer
Since we assume population variences to be eqaul, we use a pooled varience here.
using excel for the analysis,
df=n1+n2-2=18
use T.INV(0.05,18) in excel, so critical value is 1.734.
Hypothesis Test: Independent Groups (t-test, pooled variance) Central Office I Central Office II 2.168 2.362 mean 1.2735 2.3315 std. dev. 10 10 n 18 df -0.194000 difference (Central Office I - Central Office II) 3.528847 pooled variance 1.878523 pooled std. dev. 0.840101 standard error of difference 0 hypothesized difference -0.23 t .8200 p-value (two-tailed)Related Questions
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