Question

QUESTION 22 The results from a statistics class' first exam are as follows: The mean grade obtained by its 25 students is 83, with a standard deviation of 11. The distribution of grades was unimodal and symmetrical. What percentage of individuals have a z-score between -1 and 1.40 QUESTION 23 Suppose you have a tree farm and you have 1000 live oaks on this farm. You are wondering if this would be a profitable time to harvest the tallest ones – those over 55 feet tall. Your sample of 100 of them indicates that their average height is 45 feet and that the standard deviation (s) of their heights is 5 feet. Approximately how many trees in your farm to you predict will have a height greater than 55 feet? Show your work or explain how you got your answer

The results from a statistics class' first exam are as follows: The mean grade obtained by its 25 students is 83, with a standard deviation of 11.  The distribution of grades was unimodal and symmetrical. What percentage of individuals have a z-score between -1 and 1.40?

Answer 1

QUESTION 22

The results from a statistics class' first exam are as follows: The mean grade obtained by its 25 students is 83, with a standard deviation of 11. The distribution of grades was unimodal and symmetrical. What percentage of individuals have a z-score between -1 and 1.40

The p-value for z = -1 from the z-table is 0.1587.

The p-value for z = 1.40 from the z-table is 0.9192.

Required probability = 0.9192 - 0.1587 = 0.7606 = 76.06%