Chapter 3 + 4

Question 1

What is a discrete versus a continuous scale?

Answer 1

Discrete: has a sample space that can be counted like school grade= 1, 2 ,3 etc.
Continuous: a scale that includes decimals or fractions like height= 5.4 feet etc.

Question 2

What are the 4 main types of scales and describe them

Answer 2

1. Nominal
   - a scale containing individual defined categories
2. Ordinal
   - have an specific order that is clear and contain no zero point, ex. a scale where the possible choices are “never, sometimes, often and always”
3. Interval
   - have meaningful differences between each number and have no zero point, ex. calendar years, distances
4. Ratio
   - contains a true zero point where typically the values represent a magnitude

Question 3

What is a negative skew versus a positive skew?

Answer 3

In a frequency distribution graph a positive skew starts off with high values on the x-axis and tail slowly tapers down, whereas in a negative skew, the tail tapers on the left and builds to higher scores among the x-axis

Question 4

Describe kurtosis and its 3 variations

Answer 4

Kurtosis describes the steepness of a skew in its center

1. Platykurtic= relatively flat
2. Leptokurtic= relatively peaked
3. mesokurtic= in the middle

Question 5

When is pearson r used versus spearmen rho in correlation?

Answer 5

Pearson r= when both variables are relatively linearly related
spearmen rho= when n<30 and data is ordinal

Question 6

Describe reliability versus validity

Answer 6

Reliability: Refers to how the tool of measurement should remain consistent, measuring in the same way each time
Validity: Whether a test actually measures what it purports to measure

Question 7

What are the 4 main types of sampling?

Answer 7

1. Stratified
2. Random
3. Purposive
4. Incidental

Question 8

What is measurement error ? Explain the formula

Answer 8

Measurement error is the uncertainty in any given observed score. Thus, the observed score is equal to the True score plus measurement error, X= T+E

Question 9

What is systematic versus random error?

Answer 9

Systematic error influences a test in a particular and consistent direction while random error is unpredictable variations

Question 10

What is variance in relation to error ?

Answer 10

The total observed variance of a test is the true score variance plus the error variance .
Thus we can understand reliability as the proportion of true variance that makes up total variance