A suitable probability calculator can tell you the probability is about 6.7%.
_____
The standard deviation of the distribution of sample means is the population standard deviation (6) divided by the square root of the sample size (√144=12). Thus, your threshold is about (19.25-20)/(6/12) = -1.5 standard deviations from the mean.
Answer:
0.621
Step-by-step explanation:
Number of people that have run a red light in the last year = 290
Number of people that have not run a red light in the last year = 177
Total number of respondents = 290 + 177
= 467
Pr(if a person is chosen at random, they have run a red light in the last year) =
=
= 0.621
The probability that if a person is chosen at random, they have run a red light in the last year is 0.621.