Thread: Probability/Z-Score Question

For a normal distribution with a mean of 7.5 and a variance of 9, find the following:

P(x greater than or equal to 8.5)

=1 - P(Z less than or equal to (8.5-7.5)/3)

=1 - P(1/3)

1/3 on the z-score table is 0.6293

=1 - 0.6293

=0.3708

Is that correct? If not, what am I doing wrong? All help appreciated!

Originally Posted by youngb11

For a normal distribution with a mean of 7.5 and a variance of 9, find the following:

P(x greater than or equal to 8.5)

=1 - P(Z less than or equal to (8.5-7.5)/3)

=1 - P(1/3)

1/3 on the z-score table is 0.6293

=1 - 0.6293

=0.3708

Is that correct? If not, what am I doing wrong? All help appreciated!

Your answer is correct, not withstanding the lack of the use of correct notation in several places. But surely you're able to check your answer yourself using an on-line normal cdf calculator (found using Google)?