Answer:
Step-by-step explanation:
We want to find 95% confidence interval for the mean of the weight of of textbooks.
Number of samples. n = 28 textbooks weight
Mean, u =76 ounces
Standard deviation, s = 12.3 ounces
For a confidence level of 95%, the corresponding z value is 1.96. This is determined from the normal distribution table.
We will apply the formula
Confidence interval
= mean +/- z ×standard deviation/√n
It becomes
76 +/- 1.96 × 12.3/√28
= 76 +/- 1.96 × 2.3113
= 76 +/- 4.53
The lower end of the confidence interval is 76 - 4.53 =71.47
The upper end of the confidence interval is 76 + 4.53 = 80.53
Therefore, with 95% confidence interval, the mean textbook weight is between 71.47 ounces and 80.53 ounces
