Statistics Questions: Probabilities based on Poisson distributions

1. The mean life of a computer disk drive is 2,000 hours. The standard deviation is 140 hours. Assuming the life-time of the drives to be normally distributed, find the probability of a disk drive lasting more than 1,800 hours.
a. .4236
b. .9236
c. .8472
d. .5764
e. .2118
f. None of the above.

2. The yearly commissions per salesperson employed by a manufacturer of light machinery average $40,000 with a standard deviation of $5,000. What percent of the salespersons earn between $32,000 and $42,000?
a. 60.06%
b. 39.94%
c. 34.13%
d. 65.87%
e. 81.66%
f. None of the above.

3. A study of 200 stamping firms revealed these incomes after taxes:

Income After Taxes Number of Firms
Under $1 million 102
$1 million up to $20 million 61
$20 million and more 37

What is the probability that a particular firm selected has under $1 million in income after taxes?
a. 0.000
b. 0.250
c. 0.333
d. 0.510
e. None of the above.

4. A study of the opinion of designers with respect to the primary color most desirable for use in executive offices showed that:

Primary Color Number of Opinions
Red 92
Orange 86
Yellow 46
Green 91
Blue 37
Indigo 46
Violet 2

What is probability that a designer does not prefer red?
a. 1.000
b. 0.770
c. 0.000
d. 0.230
e. None of the above.

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