Posted by **pusaran** on Saturday, May 19, 2012 at 1:08am.

the academic staff of a large university are provided with a PC each. it is known that after a number of years the PC need to be upgraded. The time interval before upgrading of the PC is distributed normally with a mean of 24 months and a standard deviation of 6 month. what is the probability that:

(a) the time interval before the PC needs upgrading is more than 2 years and 6 months.

(b) the time interval before the PC need upgrading is between 23 and 27 months.

(c) the mean time interval before the PC needs upgrading is at most 25 months out of 25 PCs chosen at random.

- statistic -
**PsyDAG**, Saturday, May 19, 2012 at 11:44am
a & b. Z = (score-mean)/SD

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportions related to the Z scores.

c. Since you are dealing with means rather than individual scores, Z = (score-mean)/SEm

SEm = SD/√n

Use the same table.

I'll leave the calculations up to you.

## Answer this Question

## Related Questions

- statistic - 2. A sociologist conducted a study of divorce patterns in a ...
- university of phoenix - Does lovastatin (a cholesterol-lowering drug) reduce ...
- stats - The president of a large university wishes to estimate the average age ...
- economics - essay on staff apraisal in an organisation What kind of organization...
- math - a store has a total of 108 full-time staff and part time staff. There ...
- Statistic - A Toyota dealer wants to find out the age of their customers (for ...
- Staistcs - Problem 4 Refer again to the distribution table in Problem 3. : 3.0 ...
- STATISTICS - Bacterial samples were taken from several surfaces in a daycare and...
- Math - A fast food shop plans to employ 8 full-time staff and some part-time ...
- statistics - Before 33 33 38 33 35 35 40 40 40 31 After 34 28 25 28 35 33 31 28 ...