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Question

The following data represent the number of people aged 25 to 64 years covered by health insurance (private or government) in 2003. Approximate the mean and standard deviation for age.

 

Age         Number (millions)
25-34       27.8
35-44       30.4
45-54       31.9
55-64       24.9

 

I know that the mean is 44.69, but can anyone tell me what the standard deviation is?

 

Answer 1

I got that the mean is 115/4 = 28.75

You use the following chart to find standard deviation:    bar x = the mean

 

      x         bar x       x - bar x     (x - bar x)²

      27.8    28.75          .95            .9025

      30.4    28.75        -1.65          2.7225

      31.9    28.75        -3.15          9.9225

      24.9    28.75         3.85         14.8225

 

standard deviation = √[∑(x - bar x)²]/n      n = the number of items = 4

sd = √28.37/4 = √7.0925 = 2.66317