AP exam in math has a mean score of 73 with a standard deviation of 7.8. If one student is randomly selected, find the probability that the student's test score is less than 70.

1. A supermarket manager has determined that the amount of time customers spend in the supermarket is approximately normally distributed with a mean of 45 minutes and a standard deviation of 6 minutes. Find the probability that: a. A customer spends less than 48 minutes in the supermarket(3pts) b. Customer spends between 39 and 43 minutes in the supermarket(3pts)

a)
P(x < 48)=
P(z < (48-45)/6)=
P(z < 0.5)=0.6914 

b)
P(39 < x < 43)=
P((39-45)/6 < z < (43-45)/6)=
P(-1 < z < -1/3)=0.2108

In a normal distribution with a mean of 70 and a standard deviation of 3, what percent of the elements are between 64 and 76?

z1=(64-70)/3=-2
z2=(76-70)/3=2 
P(64 < x < 76)=
P(-2 < z < 2)=
0.9545

assume that SAT scores are normally distributed with mean u=1518 and standard deviation of 325 B) If 100 SAT scores are selected find the probability that they have a mean less than 1500

n=100
u=ux=1518
o=325
ox=325/root(100)=32.5 


P(x<1500)=
P((x-ux)/ox < (1500-1518)/32.5)=
P(z<-0.5538)=
0.2898

The mean, the median, and the mode of the five numbers below are all equal. What number does A represent? 1.8 1.6 2.1 1.7 A

sorted: 1.6, 1.7, 1.8, 2.1 


Mean = (A+7.2)/5 


the middle choices are 1.7 and 1.8. Test 1.7: 

A=5*1.7-7.2= 1.3 (no because this value leaves us without a mode) 

Testing 1.8: 

A=5*1.8-7.2= 1.8 


A=1.8 

:)

A researcher polled 230 freshman at a university and found that 110 of them were enrolled in a history class. Estimate the probability that a randomly selected freshman is enrolled in a history class

p=110/230

If mu is 68 and sigma is 4 what is the probability that x is greater then 72

Assuming normal distribution

 
 

 


:)

If the variance of the ages of the people who attended a rock concert is 22, what is the standard deviation of the ages? Round your answer to two decimal places.

Standard deviation is the square root of variance so:



:)