# Confidence Interval

Using the following information, construct a 90% confidence interval for (:1 - :2).

Sample 1: n = 8 mean = 151 standard deviation = 31

Sample 2: n=21 mean = 130 standard deviation = 72

please show results of all steps in the process.

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SEM = standard deviation / square root ('SQRT') of sample size

= 31 / SQRT(8) = 10.96

2. Calculate df:

df = n-1 = 8 -1 = 7

3. Determine t value for 90% confidence:

Use Student's t distribution table to determine t, using df =7 and α = .05

Therefore, t.05 = 1.895

Note: α = .025 because it represents either the lower or upper end of the confidence interval.

4. Use confidence interval ...