Question

The time it takes to complete one biology experiment is normally distributed with known standard deviation of 20 minutes. A random sample of 64 experiments in the science school in UCLA had a mean time of 75 minutes. Find the standard error, margin of error, and the upper and lower confidence limits of a 95% confidence interval for the population mean, m.

Answer #1

Solution :

Given that,

Sample size = n = 64

Z/2 = 1.96

Standard Error = /n

= 20 / 64

**Standard Error = 2.5**

Margin of error = E = Z/2* Standard Error

= 1.96 * 2.5

**E = 4.9**

At 95% confidence interval estimate of the population mean is,

- E < < + E

75 - 4.9 < < 75 + 4.9

70.1 < < 79.9

**Lower confidence limits = 70.1**

**Upper confidence limits = 79.9**

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