Two Way Frequency Tables
How do you find the totals in a two way table?
Add the values in the rows and in the columns
List the steps to find the linear regression of a line given a data set in your calculator.
1) Stat, Edit, Enter data in Lists 1 and 2, Quit
2) Stat again, then CALC Linear Regression (4)
or Stat, Test, LinRegTTest (if you want regression equation as well as r and r^2)
In slope intercept form, y=mx+b, this variable represents the y-intercept.
What is b?
Describe a correlation of -0.9 in terms of strength (weak, moderate, or strong) and direction.
Very strong, negative (slope of line is negative so line is going downward from left to right).
We summarized the relationship between x = height of a student (in inches) and y = number of steps required to walk the length of a school hallway, with the regression line y^=113.6−0.921x.
For this model, technology gives r = -0.632. Interpret this value.
There is a moderately strong, negative, linear correlation between a students height and the number of steps required to walk the length of a school hallway. As height increases, the number of steps required decreases.
How do you calculate percentage using a two way frequency table?
Specific number in category/total of category times 100
What variable is used to represent the correlation coefficient?
r
What does r = -0.75 tell us about a linear regression?
It has a fairly strong, negative correlation (the slope is negative so the line is going downward from left to right)
Sketch a data set with a correlation correlation of 0.98.
Show on paper or whiteboard
We summarized the relationship between x = height of a student (in inches) and y = number of steps required to walk the length of a school hallway, with the regression line y^=113.6−0.921x
Interpret the slope.
For every additional inch in height, the predicted number of steps to walk the length of the hallway will decrease by 0.921 steps.
What is a categorical variable?
a variable that takes on values that can be divided into groups or categories
What setting in MODE should you always turn on?
Stat Diagnostics
The linear model for a local store's Number of Sales people working versus Sales is as follows:
Sales = 8,106 + 91.34n (where n=# Sales People Working)
What is the y-intercept?
$8,106
A restaurant's menu items are compared in terms of correlation. Sugar versus Calories have a correlation of 0.25. Sugar versus Protein has a correlation of -0.68. Which has a stronger correlation?
Sugar versus Protein.
We summarized the relationship between x = height of a student (in inches) and y = number of steps required to walk the length of a school hallway, with the regression line y^=113.6−0.921x
Interpret the y-intercept. Is this meaningful in context?
If a student is 0 inches tall, it will take them 113.6 steps to walk the length of the hallway. This is not meaningful because a student wouldn't be 0 inches tall.
What does the "two way" is two way tables represent?
There are two different categorical variables being measured in the table
How do you quit out of any screen?
[2nd] [mode]
Round the following to the nearest hundredth: 4.567
4.57
A student says, "There was a very strong correlation of 1.22 between Sugar and Fat content." Explain the mistake made here.
Correlation must be between -1 and +1.
We summarized the relationship between x=shoe size and y=height.
For the model, technology gives r = .03. Interpret this value.
There is no relationship
What does each number in a two way table represent?
The frequency of a combination of categories
List all the information you get to see when you tell the calculator to give you a linear regression and stat diagnostics is on.
y=ax+b, a, b, r^2, and r
The linear model for a local store's Number of Sales people working versus Sales is as follows:
Sales = 8,106 + 91.34n (where n=# of Sales People Working)
What is the meaning of the y intercept, does it make sense?
No, when no one is working, there should be no sales. This is just a starting point for the data.
Two variables produce a negative correlation. How will this affect the slope?
The slope will be negative.
We summarized the relationship between x = height of a student (in inches) and y = number of steps required to walk the length of a school hallway, with the regression line y^=113.6−0.921x
For this model, technology gives r = 0.63. Interpret this value.
About 39.9% of the variability in number of steps required to walk the length of a school hallway is accounted for by the least-squares regression line with x = height (in)