Anational dental association conducted a survey to find the average (mean) amount of time dentists spend on dental fillings per week. based on a simple random sample, they surveyed 144 dentists. the statistics showed that dentists spent an average of 20 hours per week on fillings with a standard deviation of 10 hours. what is the probability of finding a sample mean less than 18 hours?

The probability of finding a sample mean less than 18 hours is 0.0082

Step-by-step explanation:

To find the probability of finding a sample mean less than 18 hours, we need to calculate the z-score of this sample mean 18. And the probability of finding a sample mean less than 18 hours is P(z<z(18)).

Z-score can be calculated as follows:

z(18)= where

Putting the numbers, we get:

z(18)=

Using z- table we can find that P(z<z(18)) = 0.0082

i found two solutions,   n = 2 • ± √3 = ± 3.4641

step-by-step explanation: