Question

The average score on a standardized test is 750 points with a standard deviation of 50 points. What is the probability that a student scores more than 850 on the standardized test?

Answer 1

convert 850 to standard z-score, then find P(Z>z) using the table of standard normal probabilities.

Answer 2

how would I convert it without knowing the total points of the test or the mean point score?

Answer 3

The mean is embedded in the question:

The--> *average score* on a standardized test *is 750 points*

Answer 4

Do you know the formula for a z-score?

Answer 5

850 points is two standard deviations above the mean (average) score of 750 points.
A simple way to solve this is to make use of the empirical rule for a normal distribution:
Approximately 95% of the data points lie within the range\[\pm2 \sigma\ of\ \mu\]
Therefore approximately 5% of the data points lie above and below the above range.
The normal distribution curve is symmetrical about the mean.
Therefore 5/2 = 2.5% of the data points lie above a score of 850.