Question

Correlation

This assignment will examine your ability to analyze the relationship between two variables, create an equation for predicting one variable from the other, and to critique the results of the data. You will be given the data for 2 psychological experiments looking at the relationship between variables. For these sets of data you will: (1) use the SPSS program to calculate the correlation and create a scatterplot (2) provide the appropriate output given from the program (3) describe this relationship (both strength and direction, and in layman's terms) (4) determine if these variables truly related or could there be a third variable at play (5) calculate the regression equation (showing your work) (6) use that regression equation to calculate a prediction; and (7) calculate the proportionate reduction in error. All work will be posted in a word document and uploaded to blackboard 1) A psychologist is investigating the relationship between drinking coffee and sleep. She chooses 20 participants and measures how many cups of coffee they had the previous day and how many hours of sleep they got the night before. The data is presented below Coffee Sleep 09.5 9.5 6 8.5 6

Answer 1

Steps to find the correlation in SPSS

Analyze -> correlate -> Bivariate -> check pearson's -> Ok

We get the following output

Coffee and sleep are negatively correlated with -0.621 coefficient of correlation.

Which implies that more the coffee less the sleep.

We have the following steps for creating a scatter plot:

Graph -> Legacy Dialogue -> Scatter plot -> Simple scatter plot ->X axis(Coffee) Y axis(Sleep) -> ok

We get the following graph

These variables might not be truly correlated a third variable might be at play which may have been the person's ability to be awake.

The regression equation is given as :

Sleep=8.564-0.3963*5=6.58 hours of sleep.