7. the times in seconds taken by an athlete to run 400 m on 7 successive days were:
53.2, 55.7, 54.2, 53.6, 59.3, 54, and 53.7
find the mean, median and standard deviation of the times
mean= (53.2+55.7+ 54.2+53.6+59.3+54+ 53.7)/7=54.81
sd=2.132
median=4
th
#=54
keep two decimals, or as many as possible
6. I travel to work by route A or route B. the probability that I choose route A is ¼.
The probability that I am late for work if I go via route A is 2/3 and the
corresponding probability if a go via route B is 1/3
a). what is the probability that I am late for work on Monday?
¼ * 2/3 +3/4 *1/3 =5/12
b). given that I am late for work, what is the probability that I went via route B?
P (B  late)= (3/4 *1/3)/ (5/12)=3/5
5. a discrete R.V. x has the following probability distribution and can only take the
values tabulated
x
1
3
6
n
12
P(x)
.1
.3
k
.25
.15
a)
find the value of k
k =0.2
b)
given that E(X)=6, find
1)
the value of n
8
2)
the variance of X
11.6
3)
E(4X)
24
4)
Var(4X)
16*11.6=185.6
5)
Sd(4X)
13.62
4. a factory produces a particular type of electronic component. The probability of a
component being acceptable is 0.95. the components are packed in boxes of 8.
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 Winter '12
 Javid
 Normal Distribution, Probability, Standard Deviation, acceptable components

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