Question

A sample of 20 paired observations generates the following data: d−d− = 1.3 and s2DsD2 = 2.6. Assume a normal distribution. (You may find it useful to reference the appropriate table: z table or t table)

a. Construct the 90% confidence interval for the mean difference μ_D. (Round intermediate calculations to at least 4 decimal places and final answers to 2 decimal places.)

Confidence interval is ________ to _________

Answer 1

Df = n - 1 = 20 -1 = 19

t critical value at 0.10 significance level with 19 df = 1.7291

90% confidence interval for D is

- t * Sd / sqrt(n) < D < + t * Sd / sqrt(n)

1.3 - 1.7291 * 2.6 / sqrt(20) < D < 1.3 + 1.7291 * 2.6 / sqrt(20)

0.29 < D < 2.31

Confidence interval is 0.29 to 2.31