I really need help on my homework!

kelsey93092

New Member
Theres 2 questions I'm really stuck on. One has three parts and is of course one of those "you can't do the next step until you get the first step" kind of thing.\

1.A set of reading scores for fourth-grade children has a mean of 25 and a standard deviation of 5. A set of scores for sixth-grade children has a mean of 30 and a standard deviation of 10. Assume that the distributions are normal.

Do you think the distributions overlap much? Explain.

2. From the previous question, the percentage of fourth-graders who score better than the average sixth-grader would be

The percentage of the sixth-graders who score worse than the average fourth-grader would be

3. Under what condition would the answers for each blank in the previous question be equal if the means can't change?

I know I'll have to compute a z-score at some point here, or perhaps a confidence interval, but I am so confused since all they have given me are the means and standard deviations. I know the mean and standard deviation of a normal distribution is 0 and 1, respectively, but I am so lost as to where to go from there.

The next problem is the same sort of thing, I am just confused as to how to get a z-score for ten percent. The closest I can find on my z-score table is .1026, am I approaching this wrong?

4. A toy factory owner plans to give pay raises this year using a normal distribution. She will make the mean raise $1000 and the standard deviation$265. Basing this on worker productivity (toys constructed), the most productive 10% of employees will see a raise of at least how much?

SmoothJohn

New Member
#1 Can you sketch the distributions? Mark the mean, and points 1,2 and 3 standard deviations from the means.
This will get you going on #2 as well.

kelsey93092

New Member
Okay, I tried to sketch the distribution, but I am unsure of how to make a good sketch if I have no data from the actual samples besides the mean and standard deviation, I guess what I mean is that I am unsure of where to plot these points.

kelsey93092

New Member
#1 Can you sketch the distributions? Mark the mean, and points 1,2 and 3 standard deviations from the means.
This will get you going on #2 as well.
Oh I got the sketch now! Now to tell what percent of fourth graders score better than sixth graders and I looking where the line for fourth graders is above that of sixth graders? Not sure how to calculate that.

SmoothJohn

New Member
Did you label the horizontal axis? What value is 1 standard deviation below the mean for each distribution?