14 the variable Z has a standard normal distribution. If P(b 18) E it is not possible for a density curve to go below the

14 the variable Z has a standard normal distribution. If

P(b

A 0.36

B 0.58

C 0.65

D 0.74

E 0.47

15 the time X that it takes people to be done sudoku puzzle follows a normal distribution with the mean 1000 seconds. It is known that approximately 99.7% of people finish puzzle I between 712 and 1288 seconds. The approximate value of the standard deviation of the distribution of X is:

A 72 seconds

B 288 seconds

C 96 seconds

D 144 seconds

E 192 seconds

16 serve speeds of players at a big tennis tournament are known to follow a normal distribution with mean 148 km/h and standard deviation 11km/h. What proportion of serves have speeds greater than 155 km/h

A 0.3636

B 0.6364

C 0.7389

D 0.2611

E 0.4168

17 monthly electric bills for houses in a large city follow a normal distribution with the mean $125 and standard deviation $18. What proportion of houses have a monthly bill between $100 and $160?

A 0.8744

B 0.8337

C 0.8126

D 0.8915

E 0.8592

18 the age when people get their wisdom teeth follows a normal distribution with mean 19.5 years and standard deviation 2.0 years. Only 1% of people get their wisdom teeth when they are older than:

A 21.48 years

B 23.60 years

C 14.84 years

D 17.52 years

E 24.16 years

19which of the following statements is false?

A Standardizing a normal variable X gives us a normal variable with mean 0 and standard deviation 1

B if X - N 88,22), then P(X=93)=0

C if X - N(9,4), and Y -N(4,9) the then density curve for Y is taller than the density curve for X

D if X has a normal distribution with mean 10 then P(X<2) = P(X>18)

E it is not possible for a density curve to go below the x axis

20 Daily sales at host a hot dog cart are known to follow a normal distribution with standard deviation $70. It is known that on 3% of days, sales are below $248.40. The mean daily sales at the hot dog cart is:

A $370

B $380

C $400

D $390

E $410