Question

Assume that when adults with smartphones are randomly selected, 44% use them in meetings or classes. If 9 adult smartphone users are randomly selected, find the probability that at least 4 of them use their smartphones in meetings or classes. 

Answer 1

Let X be number of adults who use their smartphones in meetings or classes.

Here, X ~ Binomial ( n = 9, p = 0.44 )

probability mass function of X is,

P(X = x) = ⁿC_x p^x(1-p)^n-x

We want to find, P(X >= 4)

P(X >= 4) = 1 - P(X

First we find, P(X

binomcdf

Step1) Press 2ND button then pres VARS button

Step 2) then scroll down to binomcdf and press ENTER

Insert values as follows,

trial : 9

P : 0.44

X value : 3

Paste and press ENTER we get the probability for,

P(X

Then subtract this probability from 1 we get,

P(X >= 4) = 1 - 0.384769099

P(X >= 4) = 0.615230901

Probability is 0.615230901