Recall that the standard deviation is calculated using the formula  ? =      (x − ?)2P(x)    ,  where x is the value of a random variable, ? is the expected value of x,  P(x)  is the probability of that variable, and the sum is taken for all values of the random variable. Consider the given distribution. x 0 1 2 P(x) 0.50 0.30 0.20 To simplify the calculation of ?, first determine (x − ?)2 for each value of x. Recall that we previously found  ? = 0.7. x 0 1 2 (x − ?)2 (0 − 0.7)2 =   (1 − 0.7)2 =   (2 − 0.7)2 =   B. Consider the probability distribution shown below. x 0 1 2 P(x) 0.45 0.40 0.15 Compute the expected value of the distribution. Compute the standard deviation of the distribution. (Round your answer to four decimal places.)

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Recall that the standard deviation is calculated using the formula 

? = 
 
  (x − ?)2P(x)
 
 
,

 where x is the value of a random variable, ? is the expected value of x

P(x)

 is the probability of that variable, and the sum is taken for all values of the random variable.
Consider the given distribution.

x 0 1 2
P(x) 0.50 0.30 0.20

To simplify the calculation of ?, first determine (x − ?)2 for each value of x. Recall that we previously found 

? = 0.7.
x 0 1 2
(x − ?)2
(0 − 0.7)2 =  
(1 − 0.7)2 =  
(2 − 0.7)2 =  

B. Consider the probability distribution shown below.

x 0 1 2
P(x) 0.45 0.40 0.15

Compute the expected value of the distribution.

Compute the standard deviation of the distribution. (Round your answer to four decimal places.)

C.

What is the age distribution of promotion-sensitive shoppers? A supermarket super shopper is defined as a shopper for whom at least 70% of the items purchased were on sale or purchased with a coupon.
Age range, years 18-28 29-39 40-50 51-61 62 and over
Midpoint x 23 34 45 56 67
Percent of super shoppers 10% 41% 21% 13% 15%
Compute the expected age ? of a super-shopper. (Round your answer to two decimal places.)
? =  yr
(d)
Compute the standard deviation ? for ages of super shoppers. (Round your answer to two decimal places.)
? =  yr
 
D. What was the age distribution of nurses in Great Britain at the time of Florence Nightingale? Suppose we have the following information. Note: In 1851 there were 25,466 nurses in Great Britain.
Age range (yr) 20-29 30-39 40-49 50-59 60-69 70-79 80+
Midpoint x 24.5 34.5 44.5 54.5 64.5 74.5 84.5
Percent of nurses 5.3% 9.9% 19.1% 29.8% 25.4% 8.5% 2.0%

Find the probability that a British nurse selected at random in 1851 would be 60 years of age or older. (Round your answer to three decimal places.)


Compute the expected age ? of a British nurse contemporary to Florence Nightingale. (Round your answer to two decimal places.)
 yr

Compute the standard deviation ? for ages of nurses shown in the distribution. (Round your answer to two decimal places.)
 yr

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