PSYC*4290: Psychological Measurements

Lecture 1

In 2200 BCE, what type of test was used

The Chinese Civil Service Tests

Darwin, Galton, Cattell & individual differences “Wherever you can, count.” Took place in the

1800’s

1905 was when

Alfred Binet and the Intelligence Tests was created, making it the first intelligence test

Personality tests are all the rage. So are achievement tests and standardized school testing which took place in the

1930’s & 40’s

A vocational test assesses

an individual’s interests and helps classify those interests as they relate to a job or career

An intelligence tests measures

potential to solve problems, adapt to changing circumstances, profit from experience

Personality tests look at the unique

and stable set of characteristics, traits or
attitudes

Neuropsychological tests assesses

the functioning of the brain as it relates to

everyday behaviors

An aptitude test measures the

potential for acquiring a specific skill

An achievement test measures the

previous learning and knowledge

A variable is anything that can

take on more than one value

Anything that can be different/can change either within a person or between people

Variables

Assignment of a “label” to a variable or an outcome is called a

Measurement

• Height - tall vs short

• Height - in feet and inches

These are used in

Precision

In Precision

The more precisely we measure,

the more information we have

Variables can be measured in different ways and the way we chose to measure them determines

the level of measurement being used.

In the properties of the different levels of measurement, the magnitude is the

Moreness More, less, equal

Height, age, weight

In the properties of the different levels of measurement, the Equal Intervals is the

difference between two points on a scale means the same as it

would on a different part of the scale.

Think of a roler

In the properties of the different levels of measurement, the absolute zero is the

total absence of

something

Speed, hair.... your pulse

A nominal scale has

none of these properties

and so are not really scales

Nominal scales are used for

qualitative data

⚬ Political Party, gender etc.

The ordinal scale has the property of

Magnitude

Ordinal scale allows for the

ranking, or ordering

⚬ Arranging a class by height

(without numbers)

Most scales we use are

Ordinal

Interval scales have both

magnitude and equal

intervals

⚬ Most common is temperature

⚬ Time of day on a 12 hr clock

Interval scaling

Ratio scales are

Rarely seen in social sciences

• Has all of the properties of scales

⚬ Speed of travel

⚬ Number of dogs my parents

have

Ratio scaling

Continuous is a

scale that allows for fractional amounts so decimals make sense

⚬ Height, time, distance, and age are examples of a

Continuous scale

Discrete scale is a

fixed amount which cannot be broken into smaller amounts

make sense

⚬ number of kids, people in this class, heart beats are all examples of a

Discrete scale

The more precise our measurements, the greater

our ability to use

statistics

The more precisely we measure, the less

error we have

The more complex the variable, the higher the

degree of precision we

can use in measuring

Each level has the properties of the one

before and something extra

Another name for the raw score is the

observed score

The definition for a raw score is the

The “untransformed” score before any type of operation is

performed on it.

Percentile ranks are the

Points in a distribution of scores below which

a given percentage of scores fall.

In the 45th Percentile (P45) = the score below which

45% of the other scores fall

The lower the percentile, the lower a

person’s rank within the group

What is the formula to turn a percentage rank into a raw score

Pr = (B/N) X 100

Your percentile rank is 42.5 meaning that 42.5% of students

had scores lower than yours.

What are the measures of central tendency?

The Mean, Median, and the Mode

The Mean is the

The average of the

numbers

Add the numbers together

Divide by how many

numbers were added

This is talking about the mean

The Median is the

middle number of a

sequence

Arrange the numbers in order

and find the middle

If you have an even amount

of numbers, add the middle

two together and divide by 2

This is talking about the median

The mode is the

number that occurs

most often

Find the number that occurs

most often.

This is talking about the mode

Can there be more then one mode

yes

On a perfect normal distribution, all three measures

of central tendency are located at the

same score.

A negative skew goes by

Mean, Median, Mode

A positive skew goes by

Mode, Median, and Mean

What are the measures of Variability

Consistency, Accuracy, Spread

With a small variability, scores are

1: Consistent

2:Closer to the mean

3: Less distance between scores

With a large variability, scores are

1: Inconsistent

2: Farther away from the mean

3: Greater distance between the scores

How do we measure variability

1: Range

2: Variance

3: Standard deviation

Variance and Standard Deviation indicate

how much the scores are spread out

around the mean.

When the mean is the appropriate measure of

central tendency, we compute the variance and

the standard deviation to describe

Variability

the mean is the appropriate measure

of central tendency for

normally distributed

interval or ratio scores

The standard deviation is the

approximate average deviation around the mean

The variation or how spread out or bunched up the scores are

The standard deviation

In calculating the standard deviation, the s in the formula is the

square root of the sum of the squared

differences between the observed value and the

mean, divided by the number of observations

minus one.

What is the first step one in finding the standard deviation

To find the mean of all the raw scores.

-Add them up and divide them by the total number of raw scores.

What is step two in finding the standard deviation

To take the mean of the raw scores and minus it by each of the raw scores

What is step three in finding the standard deviation

To take the scores after being minused by the mean and times them by themselves

What is step four in finding the standard deviation

To find the sum/mean of the squared scores

What is step five in finding the standard deviation

After taking the sum/mean of the squared units, we divided it by the degrees of which is typically n - 1.

-After we achieve the variance, we square root it to get the SD

The variance is simply the

standard

deviation squared.

The standard deviation is the

square root of

the variance

Find the sd for this with a sample size of 7

2.16