1: Basic Concepts

Question 1

what is a nominal scale of measurement (example)?

Answer 1

• numbers or names serve as labels
• but no numerical relationship between values
• e.g. gender, political party, religion

Question 2

what is a ordinal scale of measurement (example)?

Answer 2

• data is organised by rank
• values represent true numerical relationships
• but intervals between values may not be equal
• e.g. race position, likert scale ratings

Question 3

what is a interval scale of measurement (example)?

Answer 3

• true numerical relationships and intervals between values are equal
• but scale has not true zero point
• e.g. temperature (ºF), shoe size

Question 4

what is a ratio scale of measurement (example)?

Answer 4

• true numerical relationships, equal intervals and true zero point
• e.g. height, distance

Question 5

when should you use a median instead of a mean for a measure of central tendence?

Answer 5

Discrete or continuous data which is not normally distributed

Question 6

When should you use the mode instead of the mean?

Answer 6

categorical data

Question 7

what is the measure of spread for the median?

Answer 7

range

Question 8

define: Mesokurtic

Answer 8

• the curve of distribution is the same as normal distribution

Question 9

define: Platykurtic

Answer 9

• flatter distribution than normal distribution

Question 10

define: leptokurtic

Answer 10

• more concentrated distribution than normal distribution

Question 11

define: bimodal

Answer 11

when there are 2 peaks in the distribution

Question 12

define: uniform data

Answer 12

when everything is evenly distributed

Question 13

if there is a positive skew which side is there more data on?

Answer 13

left

Question 14

if there is a negative skew which side is there more data on?

Answer 14

right

Question 15

how to calculate a z-score

Answer 15

= (score - pop mean)/ pop standard deviation

Question 16

what do z-scores tell you?

Answer 16

Z-score indicates how much a given value differs from the standard deviation -think about 1.96

Question 17

define: sampling distribution

Answer 17

distribution of a statistic across an infinite number of samples (e.g. sampling distribution of the mean) from a population

Question 18

define: standard error

Answer 18

the standard deviation of the sampling distribution of the mean

Question 19

how to calculate standard error

Answer 19

standard deviation/ SQRT(sample size)

Question 20

what is the estimated standard error

Answer 20

sample standard deviation/ SQRT sample size

Question 21

How do we calculate the 95% CIs around a sample mean?

Answer 21

SDsample mean +/- SD * 1.96

Question 22

what do t-values show?

Answer 22

represents the distribution of sample mean differences when the null hypothesis is true. We measure the distance between our t-value value and this distribution to help us see if we can reject the null

Question 23

what is the difference between a t & p value?

Answer 23

t-value is not a probability, and therefore its value is unbounded

Question 24

what is a p-value?

Answer 24

the probability of measuring a difference of that magnitude if the null hypothesis is true

Question 25

what is the a (alpha) value?

Answer 25

threshold level of probability where we will be willing to reject the null hypothesis
– In Psychology we typically set α = .05

Question 26

should p be < or > than a to reject the null

Answer 26

p<a = reject the null
if p ≤ .05 we reject the null

Question 27

what is a type 1 error?

Answer 27

rejecting the null hypothesis when it is true

Question 28

what is a type 2 error?

Answer 28

failing to reject the null hypothesis when it is false