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 700 on the standardized test?

The average score on a standardized test is 500 points with a standard deviation of 50 points. What is the probability that a student scores between 450 and 600 on the standardized test?

The average score on a standardized test is 500 points with a standard deviation of 50 points. What is the probability that a student scores between 450 and 600 on the standardized test?


AMHD doesn't do homework. Please post your answer and someone will come along to assist.

AMHD doesn't do homework. Please post your answer and someone will come along to assist.

FYI its not homework I don't know what to do!

Not homework? Looks like it to me.

You're a school teacher trying to figure out math score spreads?

Hmmm... that depends on whether that student did his or her homework.

So the first "sigma" or standard deviation represents 34.1% (assuming a normal distribution, where we can expect a symmetric distribution about the mean). So, 34.1% of the students scored between 700 and 750 points, anther 34.1% scored between 750 and 800 points. 34.1 + 34.1 = 68.2.

This is really nice, since the problem specifically asks about a score of 700 (or higher) which matches nicely with the standard deviation given. Since the normal distribution is expected to be symmetric, there are just as many scores above the mean as below. The number of scores outside the 68.2% is simply 100 - 68.2 = 31.8. Half of these can be expected to be above the mean (and since they are outside the range of 700-800, they must also be above 800), and half below (that is, below 700). We are only interested in the percentage between 700-800 and the percentage above 800. So just add up the percentage of scores within one standard deviation of the mean (the scores between 700 and 800) and half of the percentage of scores above the one standard deviation (the number of scores above 800), and then express it as a probability.

Post what you got and maybe somebody can verify it for you.

FYI its not homework i dont know what to do!


Don't know what to do about what? These questions (I note there are two) have arisen in your personal life?

Hmm - that's not what my friends and I talk about.