Lisa, a dentist, believes not enough teenagers floss daily. She would like to test the claim that the proportion of teenagers who floss twice a day is less than 40%. To test this claim, a group of 400 teenagers are randomly selected and its determined that 149 floss twice a day.

The p value for a left tailed test would be:  

Since the p value is very higher we can conclude that the true proportion  of teenagers who floss twice a day is NOT less than 40%.

Step-by-step explanation:

Information given

n=400 represent the random sample given

X=149 represent the floss twice a day

estimated proportion of floss twice a day

is the value the proportion that we want to check

z would represent the statistic

represent the p value

System of hypothesis

We want to check proportion of teenagers who floss twice a day is less than 40%, so then the system of hypothesis are.:  

Null hypothesis:  

Alternative hypothesis:  

For the one sample proportion test the statistic is given by:

(1)  

If we replace the info given we got:

The p value for a left tailed test would be:  

Since the p value is very higher we can conclude that the true proportion  of teenagers who floss twice a day is NOT less than 40%.

what