Basic Statistical Concepts

Question 1

What are the 4 types of measurement scales?

Answer 1

Nominal
Ordinal
Interval
Ratio

(NOIR)

Question 2

What is a nominal measurement scale?

Answer 2

Nominal (name)
Qualitative measure
Gender, race, age - can, but does inherently include, ranking. Only provides information about a difference

Question 3

What is an ordinal measurement scale?

Answer 3

Ordinal (Order)
Qualitative measure
A set of ordered categories, but with no indication of how much better one score is than another
e.g. gold, silver, bronze

Question 4

What is an interval scale?

Answer 4

Quantitative
A numbered scale than CAN go below zero
e.g. temperature

Question 5

What is a ratio scale?

Answer 5

Quantitative
A numbered scale that CANNOT go below zero
e.g. blood pressure, HR

Question 6

Rati0

Answer 6

Ratio - but with a zero on the end - to remember that only rati0 has an absolute zero and interval does not

Question 7

Normal distribution

Answer 7

Symmetrical distribution of data - most subjects score in the middle
Frequency of scores decline at extremes

Question 8

What are the three measures of central tendency

Answer 8

Mean, Median, Mode

Question 9

What is the mean?

Answer 9

Arithmetic average of a set of scores - add them all together and divide by n

Question 10

What is the median?

Answer 10

Median score is where 50% of scores are above it and 50% are below it. When N is odd, median is the middle score. When N is even, N is the average of the two middle scores

Question 11

What is the mode?

Answer 11

The most frequent score in a distribution

Question 12

What is it called if a set of data has two modes?

Answer 12

Bimodal

Question 13

If data is bimodal, is it normally distributed?

Answer 13

No

Question 14

When is the mean the best reflection of the data?

Answer 14

When the data is symmetrical or normally distributed

Question 15

What are two measures of variability?

Answer 15

Standard Deviation
Range

Question 16

Range

Answer 16

Implies difference between highest and lowest score
Limitation is that it is heavily influenced by extreme scores

Question 17

Standard deviation

Answer 17

Provides information about the variation/dispersion from the mean
If mean is 10 and the SD is 2 (10 +/-2) then the majority of the data in the set is around 8-12
Data MUST be normally distributed for this to be true

Question 18

How much of the data falls within 1 SD of the mean?

Answer 18

68% - 34% either way

Question 19

What is correlation?

Answer 19

(R)
A numerical coefficient that indicates the extent to which variables are related

Question 20

Can correlation (R) signify the cause of a relationship?

Answer 20

No! It can signify the amount of relationship but not the cause

Question 21

What are the numerical values of a perfect positive, and negative, correlation respectively?

Answer 21

1.00 and -1.00

Question 22

What is Pearson’s Correlation?

Answer 22

Most common measure of correlation
Used to correlate two different variables. It is a bivariate statistic
Commonly used to establish validity

Question 23

What is validity?

Answer 23

Refers to the accuracy of a measure - HOW WELL the results measure what they are SUPPOSED to measure

Question 24

What is reliability?

Answer 24

Reliability refers to the consistency - HOW REPEATABLE are the results
Reliable = Repeatable

Question 25

Can a test be valid if it is not reliable? How about vice versa?

Answer 25

A test CANNOT be valid if it is not reliable. However, it CAN be reliable even if it is not valid

Validity includes reliability - but reliability w/o validity can be true because a test may have repeatable results, but be measuring the wrong thing

Question 26

What should R be to be considered a reliable test?

Answer 26

0.90 or higher

Question 27

What are the main sources of measurement error?

Answer 27

Instrument
Administrator
Subject
Environment