Satyagopal Mandal
Department of Mathematics
University of Kansas
Office: 624 Snow Hall  Phone: 785-864-5180
  • e-mail: mandal@math.ukans.edu
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    Some Z-Interval Problems

    Here is a collection of z-interval problems. In these problems we give the data not statistics. So, you will use the calculator.

    Z-Interval: Problems

    Ex.1: It is assumed that the lifetime (in hours) of lamps produced in factory is normally distributed with mean m and standard deviation s =1148 . A sales person claims that his lamps are better. To estimate m following data was collected on the lifetime of lamps:
     
     
     
    5110 4671 6441 3331 5055 5270 5335 4973 1837 5487
    7783 4560 6074 4777 4707 5263 4978 5418 5123 5017

    Compute a 95 percent confidence interval for the mean life time  m.
     
     

    Ex.5: To estimate the mean weight (in pounds) of salmon in a river the following sample was collected:
     
    34.7 33.8 38.2 20.3 27.8 45.3 43.1 37.3 32.5 32.3
    31.8 41.5 44.5 29.2 25.3 29.6 39.5 29.1 37.3  

    It is known that the standard deviation s = 6.5. Find a 95 percent confidence interval for the mean weight  m of salmon in the river.