Exam 7: Measures of Dispersion

Boxplots are used for preliminary data analysis.

The mean is an example of a measure of dispersion.

Observations flagged as outliers generally should be retained when they are not coding errors, when they are plausible values of the variable in question, and when they do not greatly affect the value of the mean.

The standard deviation is a desirable statistic because metric variables are normally distributed.

Values above the upper fence are defined as outliers in boxplots.

Visual representation is important for analysis and in the communication of study findings to a broader audience.

The inner fence is an observed value.

The boxplot is used with ordinal-level data.

When recoding continuous variables into ordinal-level variables, the width of categories should be equal, unless compelling reasons exist to do otherwise.

When variables are normally distributed, about 95% of observations lie ±5 standard deviations from the mean.

Frequency distributions are readily calculated by statistical software programs.

The interquartile range is defined as the distance between the first and third quartiles.

Frequency distributions describe the range and frequency of a variable's values.

The normal distribution refers to the distribution of a variable that resembles a cigar-shaped curve.

Pie charts are graphs that show the frequency of occurrences through stacks.

Skewness is a measure of whether the peak is centered in the middle of the distribution.

A histogram is similar to a stem-and-leaf plot but differs in that it shows the number of observations in each category.

Standardized variables have a mean of zero and a standard deviation of 1.