Lecture 2

Question 1

4 important things in research question?

Answer 1

1. question mark at the end
2. indicate all the constructs being investigated
3. contain the population
4. verb that indicate the type of relationship proposed (associate, predict, difference)

Question 2

3 verbal forms of relationship?

Answer 2

• associate
• predict
• difference

Question 3

in RQ:

“is there an association between studying research methods and happiness in psychology students?”

identify if this is a good RQ (use the 4 checklist for RQ requirement)

Answer 3

1. question mark
2. all constructs are listed explicitly: studying research methods and happiness
3. population: psychology students
4. verb: association

Question 4

population vs sample

Answer 4

population: complete set of all individuals relevant to RQ. size: large. often unknown
sample: subset of individuals selected from population. size: known.

Question 5

assumption in RQ regarding population & sample?

Answer 5

only one possible population and many possible samples drawn from that population

Question 6

what is a construct?

Answer 6

a construct is an unobservable attribute of people that we use in both theories and research to explain human behaviour, cognition, affect

aka: attribute / theory
eg: need for cognition

Question 7

what is a measure?

Answer 7

method for measuring people on a construct to obtain a score

aka: method
eg: need for cognition scale

Question 8

what is a score?

Answer 8

numerical value on a construct measure assigned to an individual

aka: numerical value
eg: summed responses to items in need for cognition scale

Question 9

what is raw observed scores?

Answer 9

values obtained directly from construct measure

often indicated by capital letter X, Y, etc

Question 10

what is a deviation scores?

Answer 10

transformed value from raw observed scores

value obtained by subtracting mean score form each raw observed individual score

Question 11

what does it mean when deviation score = 0?

Answer 11

means that raw score obtained is equal to mean score.

because deviation score is raw score subtracted by mean score

Question 12

benefit of deviation score?

Answer 12

helps us to identify people below and above the mean.

Question 13

characteristics of deviation score?

Answer 13

• mean of deviation score = 0
• normally lower case letter x or y
  standard deviation = standard deviation of raw scores

Question 14

what is z score?

Answer 14

standardised score whereby the deviation score is divided by the standard deviation

Question 15

characteristics of deviation score?

Answer 15

• mean of z score = 0
• standard deviation = 1
• scaling is in standard deviation units

Question 16

what is a standardised score?

Answer 16

more general version of z scores

value obtained by transforming raw score to have a PREDEFINED mean AND scaling for each unit of standard deviation.

mean and sd for standardised score are unknown. if mean = 0 and sd = 1, then it’s called z score.

hence, z score is a particular type of standardised score

eg: IQ scores (mean = 100, sd = 15)

Question 17

what is continuous random variable

Answer 17

any numerical value within defined interval (eg: 0-100)

any possible real number within the range

Question 18

what is discrete random variable

Answer 18

finite number of distinct values (eg: 1, 2, 3, 4, 5, 6)

typically indicated in integers. termed a ‘factor’ in R

also known as categorical variable (if it’s character by nature)

Question 19

what kind of variable is measured in this RQ:

“is there an association between subjective well being and optimism in students enrolled in RMHI and ARMP in 2019?”

Answer 19

swb and optimism are CONTINUOUS VARIABLE

Question 20

what kind of variable is measured in this RQ:
“is there an association between subject enrolment and type of student among enrolled students in RMHI and ARMP in 2019?”

Answer 20

subject enrolment and type of student are CATEGORICAL VARIABLE

Question 21

what differentiates the analysis involving continuous and categorical variables?

(hint: correlation / contingency table)

Answer 21

continuous = correlation to answer RQ
categorical = contingency table to answer RQ

Question 22

summary characteristic

Answer 22

• our analysis to answer RQ produce summary characteristic
• a kind of aggregation on individual scores in one or more variables to produce a single quantity (eg average)
• eg: mean, sd

Question 23

2 types of summary characteristics

Answer 23

population parameter and sample statistics

how to distinguish???
look at whom they are referring to (population or sample)

Question 24

what is population parameter

Answer 24

aggregated summary characteristics involving ALL individual from a population

Question 25

characteristic of population parameter

Answer 25

there is only ONE value of a population parameter

Question 26

what is sample statistic

Answer 26

aggregated summary characteristics from single sample drawn from a population

Question 27

characteristic of sample statistics

Answer 27

can have many sample statistics (one for each sample)

sample statistics vary from one to the next hence sample statistics are themselves random variables.

value of sample statistic is an estimate of the unknown population parameter.

Question 28

2 kinds of distributions of scores

Answer 28

population distribution and sample distribution

Question 29

characteristic of population distribution

Answer 29

there is only ONE

typically exist theoretically

Question 30

characteristic of sample distribution

Answer 30

many, one for each sample

Question 31

what is univariate distribution

Answer 31

distribution of one variable

Question 32

what is bivariate distribution

Answer 32

distribution of 2 variables

Question 33

correlation

Answer 33

measure of LINEAR SYMMETRIC association between two CONTINUOUS variables

most commonly used: pearson

Question 34

will it make a different which variable is assigned to x axis or y axis in correlation?

Answer 34

no.
cor(X, Y) = cor(Y,X)

hence, measure of association would be the same regardless of the variables assigned to which axis

Question 35

what does it mean to have positive association

Answer 35

high scores on variable 1, high scores on variable 2

Question 36

what does it mean to have negative association

Answer 36

high scores on variable 1, low scores on variable 2

Question 37

what does it mean to have no association

Answer 37

variables are uncorrelated

Question 38

what are the characteristics of correlation

Answer 38

• absolute value of correlation indicates strength of association (ignore negative or positive)
• range is 0 - 1
• weak correlation: nearer to 0
• stronger correlation: nearer to 1

Question 39

what is a correlation matrix

Answer 39

a table/matrix that indicates correlation of 2 or more variables. the rows indicate the set of variables column indicate the set of variables in the other variable.

Question 40

what is correlation plot

Answer 40

table/matrix in which each individual cell refers to the correlation between 1 variable and another.

colour intensity signifies the strength (darker means stronger)
colour (red or blue) signifies direction (red is positive)

helpful to see pattern (instead of numbers)

Question 41

population vs sample correlation coefficient

Answer 41

p (rho) for population correlation

r for sample correlation (vary from one sample to the other). used as estimate for population.

Question 42

what is the effect of sample size to sampling distribution?

Answer 42

shape and spread of distribution (aka graph) depends on the sample size.
the bigger the sample size, the smaller the variability, less spread.

Question 43

what is standard error

Answer 43

measure of variability of a sample statistic.