KEY FEATURES: Introduces students to developing research questions and shows their importance in driving research design. Rarely taught topics, such as how to enter and clean data, offer students information missed in both research methods and statistics courses. Shows how to write up survey results for academic, business and nonprofit reports to alleviate the confusion students feel about how to write up findings. Rigorous treatment of sampling focuses on many sampling issues from probability theory to weighting. Offers the process of actually conducting a survey with advice on administering surveys, incentives, and improving response rates.

# How Do We Examine Variation in Continuous Variables When Using the Mean?

### How Do We Examine Variation in Continuous Variables When Using the Mean?

With the mean as the measure of central tendency, the variance and standard deviation are the best measures of dispersion to use. Again, measures of dispersion show us how spread out responses on a variable are. “Variance” is defined as the average squared deviation of each response from the mean of the variable (or $Var\text{\hspace{0.17em}}\overline{x}=\frac{\sum {\left({x}_{i}-\overline{x}\right)}^{2}}{N}$). The standard deviation is calculated as the square roaot of the variance. What’s nice about the standard deviation is that it is in the same units as the mean: $SE\text{\hspace{0.17em}}\overline{x}=\sqrt{Va{r}_{\overline{x}}}$.

If our variable is distributed normally (symmetrical bell curve), then the standard deviation provides important information about the distribution of responses under the bell curve. One hundred ...

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