2022 Introduction to Statistics in Research Mitchell 2nd ed

I N T R O T O R E S E A R C H : D A T A V I S U A L I Z A T I O N & C O M M O N S T A T T E S T S

Practice, practice, practice…. Using descriptive statistics and z scores

The following data set is new-born birth weights categorized by mothers who smoked and mothers who never smoked.

Answer the following questions – using Descriptive Statistics in Excel

1) Find the mean and median for both groups. Are they the same or very different?

2) Find the range and standard deviation. Which data set shows more variability.

3) Determine the z-score for a 9 pound newborn in both categories. Explain what it means.

4) Could you conclude from these data that smoking causes lower birth weights?

Table 71: Birthweight of infants from both smoking and non-smoking mothers

To answer the questions review the Excel output using descriptive statistics.

Q1: The means and medians were very similar when you compare WITHIN the group. It appears that newborns from the "mother never smoked" group tends to weigh a half- pound more. Q2: The birth weight in newborns for "mother never smoked" is slightly more variable (1.26) compared to (1.06) of "mother smokes". Q3: Determine the z-score for a 9 pound newborn in both categories. Explain what it means.

Table 72: Descriptive Statistics from Excel Output

First, let’s review the formula:

Equation 4: Formula for Z

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