2.1 – Describing Location in a Distribution
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Transcript of 2.1 – Describing Location in a Distribution
2.1 – Describing Location in a Distribution
Day 1 on Assignment Guide
Percentiles
• The percent of observations in a set of data that are below a certain value.
• It is possible to include equal to, but we will strictly do below for consistency
Cumulative Relative Frequency Plot
• Remember relative frequency is percent• Cumulative – running total
AKA “Ogives”
Shape for Cumulative Relative Frequency Plot
Where is the graph the steepest?
What does this mean?
Sketch a Cumulative Relative Frequency Plot for
this data. Describe the shape.
Sketch a Cumulative Relative Frequency Plot for symmetric and skewed left
Check Your Understanding
Turn to page 89 and do problems 1 – 4We will do one at a time on the whiteboards
z-scores
• Also called standardized value• It is unit-less• Tells us how many standard deviations away
from the mean a particular value is• Formula is on your formula sheet and on p. 90
In 2009, the mean number of wins in MLB was 81 with a standard deviation of 11.4 wins.
1. Find and interpret the z-score for the NY Yankees if they had 103 wins.
2. Find and interpret the z-score for the NY Mets if they had 70 wins.
1. z-score = (103-81)/11.4 = 1.93. Interpret: The NY Yankees were 1.93 standard deviations above the mean number of wins.
2. z-score = (70-81)/11.4 = -0.96. Interpret: The NY Mets were 0.96 standard deviations below the mean number of wins.