Week2 Flashcards
What is the purpose of descriptive statistics?
To summarize and interpret data using frequency distributions and measures of central tendency.
Why do we need measures of variability in addition to central tendency?
Measures of central tendency show the center of a data set, but variability shows how data points spread around this center.
What is the range in a data set?
The difference between the maximum and minimum values.
What is a limitation of using range to measure variability?
It is highly sensitive to outliers, which can distort the spread of data.
How is the inter-quartile range (IQR) calculated?
By subtracting the 25th percentile from the 75th percentile, focusing on the middle 50% of data.
What is the purpose of trimming data?
To reduce the influence of extreme scores, especially in skewed data.
What is variance?
The average of the squared differences between each data point and the mean.
How do you calculate variance?
1) Find the mean. 2) Subtract the mean from each data point and square the result. 3) Find the average of these squared differences (divide by N-1).
What is standard deviation?
The square root of the variance, indicating the spread of data around the mean in original units.
What does a large standard deviation indicate about a data set?
The data points are widely spread around the mean.
What is a z-score?
A measure of how many standard deviations a data point is from the mean.
How is a z-score calculated?
Z = x - mean/ standard deviation
Why are z-scores useful?
They help identify outliers and assess a data point’s position within a distribution.
When is a data point considered an outlier based on z-scores?
If it is more than 3 standard deviations away from the mean.
What type of variability measure ignores extreme values in data?
The inter-quartile range (IQR).
