Mean Girls
This symbol represents the population mean.
What is μ (mu)?
In the weighted mean formula, this is what always goes in the denominator.
What is the sum of the weights?
This measure of location is defined as the value that occurs most often in a data set.
What is the mode?
This is the simplest measure of dispersion, calculated as maximum minus minimum.
What is the range?
This rule applies only to symmetrical, bell-shaped distributions and estimates the percentage of values within 1, 2, and 3 standard deviations of the mean.
What is the Empirical Rule (or Normal Rule)?
This is the denominator in the formula for calculating a sample mean: the number of values in the sample.
What is n?
This is the general term for the numbers (like hours worked or units sold) that get multiplied by each value before summing, in a weighted mean.
What are the weights?
This is the minimum scale of measurement required to compute a median.
What is the ordinal scale?
This is what you get when you take the square root of the variance.
What is the standard deviation?
Under the Empirical Rule, this percentage of values falls within 1 standard deviation of the mean.
What is about 68%?
This is always true about the sum of deviations of each value from the mean.
What is "it equals zero"?
The weighted mean is a convenient shortcut to use when several observations share this property.
What is the same value?
Unlike the mean, the median is NOT influenced by these.
What are extreme values (outliers)?
When computing sample variance, you divide by n − 1 instead of n for this reason.
What is "to correct for the tendency of n to underestimate the population variance"?
In a distribution where the mean, median, and mode are all equal and located at the same point, this describes the shape of the distribution.
What is symmetrical (bell-shaped)?
This is the one weakness of the mean — it gets pulled around by these kinds of values.
What are extreme values (outliers)?
At Carter Construction, 14 employees earn $16.50/hr, 10 earn $19.00/hr, and 2 earn $25.00/hr. This is the weighted mean hourly wage.
What is $18.12, approximately?
For a data set with an even number of values, this is how you find the median.
What is: average the two middle values?
For traffic citation data with a population variance of 124 citations², this is the standard deviation (to two decimals).
What is 11.14 citations?
In this type of skewed distribution, the mean is pulled out toward the left tail, landing to the left of both the median and the mode.
What is a negatively skewed (left-skewed) distribution?
For the I-75 exit distances in Kentucky (46 exits, a total of 192 miles), this is the population mean to two decimal places.
What is 4.17 miles?
At Loris Healthcare, 50 aides earn $12/hr, 50 practical nurses earn $20/hr, and 100 registered nurses earn $29/hr. This is the weighted mean hourly wage across all 200 staff.
What is $22.50?
In a positively skewed distribution, the mean, median, and mode line up in this order from left to right.
What is the mode, median, mean?
For hourly wages of $12, $20, $16, $18, and $19 (mean = $17), this is the sample standard deviation.
What is $3.16?
In a distribution where the mode sits at the peak, the median is just to the right of it, and the mean is pulled even further right, this describes the direction of skew.
What is positively skewed (skewed right)?