More Practice Problem ANSWERS: Correlation

Item 5

How much variance is NOT accounted for between these two variables:

Strength   Anxiety 
    2                     3 
    9                     7 
    3                     4 
    1                     1 
    7                   12

SSx =     47.20
SSy =     73.20
SSxy =   47.20
r =              .80
r² =       .65 or 65%

1 – r² = .35 or 35%

Item 6

Is there a significant relationship between the number of petals on a flower and how much the elephant plant weighs:

Petals      Weight 
  18                     1 
  15                     7 
    8                   11 
    6                     6 
    4                   18 
    2                   22

SSx =  200.83
SSy =  310.83
SSxy = – 211.17
r =  - .85
r² = .71
Check r against the Critical values of the Pearson r table using 4 degrees of freedom = .811
Since r of .85 is larger than the table r of .81, this correlation is significant and the relationship you see is not likely to be due to chance.

Item 7

What percent of variance do love and peace have in common:

Love          Peace 
 12                     1 
 22                     3 
   8                     0 
 19                     1 
   2                   11 
   9                     4 
   7                     5

SSx =    295.43
SSy =      83.71
SSxy = - 92.14
r =  - .59
r² = .34 or 34% of the variance in common

NOW YOU CHOOSE:
    Day 5: Correlation
    Bit More About Correlation
    Even More About Correlation
    Calculate Correlation
    Practice Problems
    More Practice Problems
    Word Problems
        Sim1            Sim2             Sim3
        Sim4            Sim5             Sim6
        Sim7            Sim8             Sim9
    Basic Facts About Correlation
    Vocabulary
    Formulas
    Quiz 5
    Summary