i need help: A national achievement test is administered annually to 9th graders. The test has a mean score of 100 and a standard deviation of 15. If John’s z-score is 1.20, what was his score on the test?
118
To find John's score on the national achievement test, we can use the formula for z-score:
z = (x - μ) / σ
where z is the z-score, x is the score, μ is the mean, and σ is the standard deviation.
Given that John's z-score is 1.20, and the mean is 100 with a standard deviation of 15, we can rearrange the formula to solve for his score:
1.20 = (x - 100) / 15
To isolate x, we can cross-multiply:
1.20 * 15 = x - 100
18 = x - 100
Now, we can solve for x:
x = 18 + 100
x = 118
Therefore, John's score on the national achievement test was 118.