Quandaries and Queries


Hello, I am a Senior from Florida and I have a really hard general statistics class. I would like to know if you guys can help me with these two problems
I am having problems with these two questions:
   Find the standard deviation of the given data set

  1. To get the best deal for CD dealer, Jessica called  eight appliance stores and asked the cast of a specific model. The prices she quoted are listed below.
    $300, $203, $272, $332, $440, $119, $129, $254
  2. Use the binomial probabilty formula to find the indicated probability. A company finds that an average  of 20% of all new employess resign during the first year. Find the probabilty that among the next 30  employess hired, exactly five resign  during the first year (n=30, x=5, p=5, = 0.2, q=0.8)




Hi Urial,

Here is a solution to the first problem. There are a number of equlvalent expressions for the variance V of a data set. The expression I find most useful is

V = [n times (the sum of the squares of the x's) - (the sum of the x's squared)] all divided by n times (n-1)

You have 8 observations so n = 8.

The sum of the x's is 300 + 203 + ... + 254 = 2049 thus
the sum of the x's squared is 20492 = 4198401

The sum of the squares of the x's is 3002 + 2032+ ... + 2542 = 604335

Hence the variance is

V = (8 * 604335 - 4198401)/(8*7) = 11362.1

The standard deviation is the square root of the variance and hence

standard deviation = Sqrt(11362.1) = $106.59



Go to Math Central