1) 1. You are interested in determining the difference in two population means.
ID: 3314643 • Letter: 1
Question
1)
1. You are interested in determining the difference in two population means. You select a random sample of eight items from the first population and eight from the second population and then compute a 95% confidence interval. The sample from the first population has an average of 12.2 and a standard deviation of 0.8. The sample from the second population has an average of 11.7 and a standard deviation of 1.0. Assume that the values are normally distributed in each population. The point estimate for the difference in means of these two populations is ______.
-0.2
0.2
0.5
-0.5
0.06
2)
1. A researcher wishes to determine the difference in two population means. To do this, she randomly samples nine items from each population and computes a 90% confidence interval. The sample from the first population produces a mean of 780 with a standard deviation of 240. The sample from the second population produces a mean of 890 with a standard deviation of 280. Assume that the values are normally distributed in each population and that the population variances are approximately equal. The critical t value used from the table for this is
1.860
1.734
1.746
1.337
2.342
-0.2
0.2
0.5
-0.5
0.06
2)
1. A researcher wishes to determine the difference in two population means. To do this, she randomly samples nine items from each population and computes a 90% confidence interval. The sample from the first population produces a mean of 780 with a standard deviation of 240. The sample from the second population produces a mean of 890 with a standard deviation of 280. Assume that the values are normally distributed in each population and that the population variances are approximately equal. The critical t value used from the table for this is
1.860
1.734
1.746
1.337
2.342
Explanation / Answer
1. point estimate for differences between means
= First sample mean - Second sample mean
= 12.2 - 11.7
= 0.5
Option C is correct.
2. Degrees of freedom = n1 + n2 - 2 = 9 + 9 - 2 = 16
Hence,
Critical t value = 1.746
Option C is correct.
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