Arecent study of the lifetimes of cell phones found the average is 24.3 months. the standard deviation is 2.6 months. if a company provides its 33 employees with a cell phone, find the probability that the mean lifetime of these phones will be less than 23.8. assume cell phone life is normally distributed variable.

Answer is 0.1357

Step-by-step explanation:

Let X represent the lifetimes of cell phones.

Given that X is normal with mean = 24.3 and std dev = 2.6

Sample size = 33

Hence std error of sample = 2.6/sq rt 33

=2.6/5.74

=0.453

When x Is normal we have

(x-24.3)/0.453 ~(N(0,1)) i.e. Z variate

P(X<23.8) = P(Z<-0.5/0.453) = P(Z<-1.10)

=0.5-0.3643

=0.1357

y=mx+

1. d.90

2. e. none of these (80)

3. a. 0

4. b. 6

5. e. none of these (10)

6. a. 5