Question

According to an information technology advisory firm, 45% of mobile phones worldwide use a certain operating system in 2013. A random sample of 21 mobile phone users was selected in 2013. Use the normal approximation to the binomial distribution to answer parts a through e below. a. Calculate the mean and standard deviation for this distribution. u (Type an integer or a decimal.) (Round to two decimal places as needed.) = b. What is the probability that 11 or more of the 21 mobile phone users have this operating system? (Round to four decimal places as needed.) c. What is the probability that exactly 12 of the 21 mobile phone users have this operating system? (Round to four decimal places as needed.) d. What is the probability that 5, 6, or 7 of the 21 mobile phone users have this operating system? (Round to four decimal places as needed.) e. What is the probability that 12, 13, or 14 of the 21 mobile phone users have this operating system? (Round to four decimal places as needed.)

Answer 1

a)

u	9.45
sd	2.28

b) Answer: 0.2483

x	11
Using(x-u)/sd	0.679883
Normal table	0.751711
step 1-0.751711	0.248289

c) Answer: 0.1166

x	11	12
Using(x-u)/sd	0.679883	1.118518
Using Normal table	0.751711	0.868327
Difference	0.11662

d) Answer: 0.1329

x	4	7
Using(x-u)/sd	-2.39056	-1.07465
Using =normsdist(z)	0.008411	0.141265
Difference	0.13285

e) Answer: 0.2253

x	11	14
Using(x-u)/sd	0.679883	1.995787
Using =normsdist(z)	0.751711	0.977021
Difference	0.22531