Statistics with Probability

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  • #12778

    Ezra Halleck
    Participant

    The first part of the course is known as descriptive statistics. In Chapter 2, we learn about how to collect, organize and display data. In chapter 3, we encounter measures of central tendency, such as median and average, as well as of dispersion, mainly standard deviation.

    In these discussion boards, please discuss homework problems and ask questions.

    #15356

    Ezra Halleck
    Participant

    One student has asked for the procedure for making a histogram.
    1. decide on the number of bins and bin width. A rough equation is:
    #bins * bin width = range = max-min+1
    So for instance if your min is 31 and your max is 150, then your range is 120. If you want 8 bins, then your bin width should be 120/8=15
    2. Decide on your right boundaries. For the same example, they would be 45, 60,…,120 and put them in a column “bins”
    3. Label the next column to the right of the bins_array with “frequencies”
    4. Select the cells to the right of your bins and type “=frequency(data_array, bin_array)” where you click on the first element in each array and then shift-click on the last element in your array. Be sure to put a comma in between each input. If at any point, the target cells are not all selected then you need to start step 4 again.
    5. Do not press enter, instead press shift-ctl + enter. As a check that you have done step 4 correctly, the frequencies should sum to number of data points.
    6. With the frequencies selected, create a column graph going to the insert tab, adjust the horizontal axis in “select data”
    and double click on a column to reduce the gap between the columns to a few percent.

    #15564

    Ezra Halleck
    Participant

    could you tell me what the difference between STDEV and SQRT in excel?
    thanks!

    I suggest that you use the help resources of Excel. If you look up sqrt or stdev, you will get plenty of information. I will just comment on how it fits in with what we have done. The standard deviation is defined to be the square root of the variance, so if you have calculated the variance, you can just take the square root (SQRT) to find the standard deviation. You may also calculate the standard deviation (STDEV) directly inputting the data.

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