Question

Need help on question 5(b);5(c);5(d)
Paper: https://dl.dropbox.com/u/63664351/Mathematics%20at%20A-level%20ver3.pdf
Let first talk about 5(b).

Answer 1

Problem: 5(b)
A certain computer simulation generates a random amount of data whenever it runs. On average it creates 30Mb of data, with a standard deviation of 5Mb. The simulation is run 64 times. Let D be the random variable for the total amount of data generated.
(i) Find E(D)
(ii) Find Var(D)
(iii) Using a normal approximation, estimate the probability that the data will overflow the computer’s 2000Mb storage disc.

Attempted solution:
(i) E(D)=nu=64*30=1920
(ii)Var(D)=n σ^2=64*5^2=64*25=1600

Question: I don't know how to find part (iii)

Topic: Central Limit Theorem?

Answer 2

Expected value = mean.
Variance is the square of the standard deviation.
for (iii), use x=2000 and calculate a z-score.

Answer 3

That's it. I don't know how to calculate z-score? What is t-table?

Answer 4

You can find formulas and tables here.
http://stattrek.com/statistics/formulas.aspx

Answer 5

so many