1. The heights of males students at have a nearly normal distribution with = 70

Question

1. The heights of males students at have a nearly normal distribution with = 70 inches and a standard deviation of = 2.8 inches. If 35 male students are randomly selected to make up an intramural basketball team, what is the probability that the heights of the team will average over 72 inches? Answer: 0.0002) how to get this answer?

2. Suppose that 20% of young adults who shop online own a mobile phone with Internet access. Suppose you selected a random sample of 200 young adults who shop online and let X be the number who own a mobile phone with Internet access.

Find the probability that the number of young adults who own a mobile phone with Internet access is less than or equal to 50. (Answer: 0.969) (howo to do this)

3.

A random sample of size 150 is taken from a population that has a mean = 60 and a standard deviation of = 8. The population distribution is unknown.

Is it reasonable to conclude a normal distribution for the sample mean ? Explain why or why not.

Find the probability that lies between 59 and 61. (Answer: 0.974) how to do this

Explanation / Answer

Mean is 70 and s is 2.8

standard error is given as s/sqrt(N)=2.8/sqrt(35)=0.47329

z is (x-mean)/SE

P(xbar>72)=P(z>(72-70)/0.47329)=P(z>4.23) or 1-P(z<4.23)

from normal distribution table we get 0.0002

Using Excel :=1-NORM.DIST(72,70,0.47329,TRUE)= 1.19079E-05

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