You measure 28 textbooks' weights, and find they have a mean weight of 36 ounces. Assume the population standard deviation is 6.5 ounces. Based on this, construct a \( 90 \% \) confidence interval for the true population mean textbook weight.
Give your answers as decimals, to two places

Answer

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Answer

Upper = x̄ + E = 36 + 1.645 * (6.5 / \sqrt{28})

Steps

Step 1 ：n = 28

Step 2 ：x̄ = 36

Step 3 ：σ = 6.5

Step 4 ：CI = 90\%

Step 5 ：z = 1.645

Step 6 ：E = z * (σ / \sqrt{n})

Step 7 ：Lower = x̄ - E = 36 - 1.645 * (6.5 / \sqrt{28})

Step 8 ：Upper = x̄ + E = 36 + 1.645 * (6.5 / \sqrt{28})