Asconting to a recent national Gallup Pell of U.S. smartphone users, 57\%

Douglas Kraatz

Douglas Kraatz

Answered question

2021-11-18

Asconting to a recent national Gallup Pell of U.S. smartphone users, 57% upgrede their cell phone every two years.
Use this information to answer the following questions. Show all work. Be sure to include your probability and calculator statements for the questions where indicated.
Determine the probability (to 4 decimal places) that:
A. exactly 8 users out of 15 smartphone users do not upgrade their cell phones every two years.
Probability statement:
[State question using probability notation:P( )]
Calculator Function w/values:
[List TI calculator function with values used to solve this problem.]
B. at most 7 users of 15 smartphone users upgrade their cell phones every 2 yeas.
Probability statement:
[State question using probability notation: P( )]
Calculator Function w/values:
[List TI calculator function with values used to solve this problem.]
C. between 10 and 12 users, inclusive, of the 15 smartphone users do not upgrade their cell phones every two years.
Probability statement:
[State question using probability notation: P( )]
Calculator Function w/values:
[List TI calculator function with values used to solve this problem.]

Answer & Explanation

SaurbHurbkj

SaurbHurbkj

Beginner2021-11-19Added 16 answers

A.
Denote X as the number of smartphone users, out of the n randomly selected users, who upgrade their cell phone every two years. Here, n=15. Assume that the decisions of the users regarding changing their smartphones as independent of each other. The probability that a smartphone user upgrades their cell phone every two years is a constant, p=0.57, that is, 57%. Consider it to be a success if a smartphone user changes their smartphone every two years. Thus, X has a binomial distribution with parameters, n=15, p=0.57,
Since changing smartphone every two years is considered a success, not changing smartphone every two years is failure. The probability of failure is, q=0.43(=10.57)=1p. Denote Y as the number of failures in the n=15 trials. Then, Y=nX. The distribution of Y is binomial with parameters, n=15, q=0.43.
The probability statement to find the probability that exactly 8 out of the 15 smartphone users do not upgrade their cell phones every two years is P(Y=8).
The TI-83 calculator command to find the probability is of the form: binompdf (n,p,x).
For the distribution of Y, the probability parameter is 0.43, so that one must replace 0.43 in place of p.
Press 2nd > VARS to open the “DISTR” menu.
Scroll to reach the binompdf function, and press Enter.
Enter 15,0.43,8, close the bracket and press Enter.
The probability value corrected to 4 decimal places is 0.2898.
kayleeveez7

kayleeveez7

Beginner2021-11-20Added 10 answers

B.
The probability statement to find the probability that at most 7 users of 15 smartphone users upgrade their cell phones every 2 years is P(X7).
The TI-83 calculator command to find the less-than type cumulative probability is of the form: binomcdf (n,p,x).
For the distribution of Y, the probability parameter is 0.57, so that one must replace 0.57 in place of p.
Press 2nd > VARS to open the “DISTR” menu.
Scroll to reach the binomcdf function, and press Enter.
Enter 15,0.57,7, close the bracket and press Enter.
The probability value corrected to 4 decimal places is 0.2898.
Don Sumner

Don Sumner

Skilled2021-11-23Added 184 answers

C.
NSK
The probability statement to find the probability that between 10 and 12 users, inclusive, of the 15 smartphone users do not upgrade their cell phones every two years is P(10Y12)
The probability statement can be written as follows:
P(10Y12)
=P(Y12)P(Y<10)
=P(Y12)P(Y9).
Using the command binomcdf(15,0.43,12),P(Y12)=0.9993 (correct to 4 decimal places).
Using the command binomcdf(15,0.43,9), P(Y9)=0.9435 (correct to 4 decimal places).
Thus,
P(10Y12)
=P(Y12)P(Y9)
=0.99930.9435
=0.0558
The probability value corrected to 4 decimal places is 0.0558.

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