- There is no “true zero level”. This means that lets say a person takes an
intelligence test and gets zero, we cannot say that the person has zero intelligence
because if the test was easier they would have gotten a higher score. Therefore
there are no zero levels in psychology.
- ‘Absolute amount of a variable’ – for example how intelligent someone is. We
cannot measure the absolute amount of a variable in a person.
- In psychology we can still measure given traits in a person. One way of doing this
is by rank. We can rank people from most rebellious to least rebellious and put
them in 1st, 2nd, 3rd place.
- The issue is that the person in first place may only be slightly more rebellious
than the person in 2nd place, and the 2nd place may be much more rebellious than
3rd place therefore it is hard to determine an average. The differences between
each place or “score” must be MEANINGFUL. Therefore each difference must be
the same (equal intervals)
• Equal diff / intervals between scores represent roughly equal diff in the level of the
Eg) diff b/w IQ 120 and 130 has same meaningful diff as diff b/w 140 and 150.
• Standard scores – enables to make meaningful comparisons across diff kinds of
Eg) how far below or above avrg on for one trait vs other
- The measurements are not taken in a specific unit. We must come up with a way
to compare two different variables. For example, if your IQ is 90 and the average
is 100, and your average sociability score is 60 and the average is 50, we must be
able to understand that although 60 is lower than 90, the sociability score is
HIGHER than the IQ. These two scores are on different scales.
- Basically in order to compare two scores, you have to change both scores into
STANDARD SCORES so that you can compare properly.
- Take the persons score and subtract the AVERAGE SCORE from it. If the
outcome is a positive number, they are above average, if it is a negative number,
they are below average.
• But must also take variablitiy into consideration. So devide diff from person’s score to
avg score by st dev.
- After making the comparison we want to see how FAR a person is from the
mean. Are they WAY above or below average, or not too far off?
- Take the sum from the first step and divide it by the standard deviation.
- STANDARD DEVIATION PAGE 4
- The standard score is a universal value.
• Standard score mean = 0, st dev = 1
• Correlation coef
- Known by the symbol “R”
- Values range from -1 to +1. -1<r<+1
- No correlation = 0.
- correlate two variables to each other
- variable: quality that varies quantitatively between diff entities
- indicates strength & direction of the relationship