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Descriptive Statistics

Descriptive Statistics. Open the dataset ‘ ex02-01.mtp ’ using File  Open Worksheet . Data of breaking strength of wood (lbs). We will use Minitab’s descriptive statistics module to calculate the mean, standard deviation, interquartile range and the five-number summary .

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Descriptive Statistics

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  1. Descriptive Statistics • Open the dataset ‘ex02-01.mtp’ using File Open Worksheet. • Data of breaking strength of wood (lbs). • We will use Minitab’s descriptive statistics module to calculate the mean, standard deviation, interquartile range and the five-number summary.

  2. Descriptive Statistics • First calculate the mean, std dev and IQR. Select Stat  Basic Statistics  Display Descriptive Statistics Select strength as the Variable. Click on the Statistics button

  3. Descriptive Statistics Select Mean, Standard Deviation and Interquartile range Make sure you unselect any of the other statistics Click OK twice. Descriptive Statistics: strength Variable Mean StDev IQR strength 30841 3019 2473

  4. Five-Number Summary From the menu bar select Stat  Basic Statistics  Display Descriptive Statistics In the window, select strength as the variable click the Statistics button

  5. Five-Number Summary Select First quartile  Median  Third quartile  Min  Max click OK twice

  6. Five-Number Summary Descriptive Statistics: strength Variable Minimum Q1 Median Q3 Maximum strength 23040 30243 31975 32715 33650

  7. Box Plot • The box plot in Minitab is constructed in the standard way: • The box is the interquartile range (IQR ) • 1st quartile is lower horizontal line and 3rd quartile is upper horizontal line • The line in the middle of the box is the median (Q2 or 50th percentile). • The whiskers represent 1.5 x IQR for the upper and lower. • The IQR is a robust estimate of dispersion and is ~1.35. • The asterisk (*) represents an outliervalue.

  8. Box Plot • Open the dataset ‘ex02-12.mtp’ • Data of counts of trees for different plots. • A Box plot using theWith Groupsoption is used to examine the location and dispersion of a variable with several categories.

  9. Box Plot Select Graphs  Boxplot from the menu bar. In the Boxplots window select One Y, With Groups. Click OK

  10. Box Plot Select trees for the Graph variable Select group for the Categorical variable click OK

  11. Box Plot

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