ch02 strong VS weaker relationships

p16

 

Envelop things

 

In a perfectly consistent relationship, each score on one variable is paired
with only one score on the other variable.

some degree of consistency ... tend to change in a consistent fashion.

The degree of consistency in a relationship is called strength, and a less
consistenct relationship is called a weaker relationship.

part A
1) same amount time does not receive same error score
2) same amoutn error score have differnt study time
Nonetheless, a resonably clear pattern is still here in which one batch of  

-- this is why the histogram is used sect the region first--

similar error scores tends to occur at one study time, but a different,
lower batch of similar error scores tends to occur at the next study time.
Therefore, this is a reasonably strong relationship.

part B
1) time paired with a wider range error scores
2) same error score with a greater variaty
These aspects produce greater overlap between the error scores at one study
time and those at the next, so there is closer to the same batch of error
scores at each study time. This produces a pattern of decreasing errors that
is harder to see.

The strength of a relationship is the extent to which one or close to one
value of Y tends to be consistently associated with only one value of X.

REMEMBER A stronger relationship occurs the more that one group of similar Y
scores is associated with one X score and a different group of similar Y
scores is associated with the next X score

Why the differences even the variable have the strong relationship
1) extraneous influences(big or small noise)
2) individual differences

REMEMBER Research is concerned not only with the existence of a relationship but also with the strength of the relationship.