Apendix

Question 1

descriptive statistics

Answer 1

descriptive statistics quantitatively describe a population or set of data.

provide information about the data involved in the study.

example : number of subjects, proportion of subjects of each sex, average age.. etc… whatever relevant to the study.

Question 2

What does descriptive statistics include?

Answer 2

measures of central tendency ( such as mean median mode)

measures of variability ( such as range and standard deviation)

Question 3

Measures of central tendency

Answer 3

it summarizes or describes the entire set of data in some meaningful way.

Question 4

Mean

Answer 4

Mean is the average of a given sample

it can be both useful and deceptive. Since it usually does not account for the most accurate understanding of the whole group. example, if 10 people in a group earns minimum wage and one person is a billionaire, then the mean would resemble a number by which we will understand everyone is wealthy.

Question 5

Median

Answer 5

It is the middle number in a data set.

Put the numbers in a consecutive order and then find the middle number.

ODD number of numbers : there will be a single number that will be the median

EVEN number of numbers : median is determined by averaging the two middle numbers.

Usefulness : in finding the midpoint of the data, but does not say much about the outliers. It will give a good idea about the salaries of the 10 person but will not include the billionaire persons salary.

Question 6

Mode

Answer 6

most frequently recurring number in the data.

if there are no numbers that occur more than once, then there is no mode. if there are multiple numbers that occur most frequently, each of those numbers is a mode.

modes are never averaged.

Mode is particularly useful in describing scores, e.g. test scores.

Question 7

Range

Answer 7

the range is the difference between the smallest and the largest number in a sample.

Question 8

Standard Deviation

Answer 8

It is the degree of variation from the mean.

The standard deviation is more useful than the range for calculating how much the data vary.

it can determine if the numbers are packed together or dispersed because it is a measure of how much each individual number differs from the mean.

Question 9

Normal distribution

Answer 9

very important in the study of human behaviour.

large sets of data e.g. height, weight, often form a symmetrical bell shaped distribution when graphed by frequency.

Question 10

Frequency

Answer 10

number of instances.

Question 11

what does a low standard deviation indicate?

Answer 11

It reflects that data points are all similar and close to the mean.

A high standard deviation indicate that the data are more spread out.

Question 12

Example of normal distribution and standard deviation

Answer 12

look at book page 299 and 300

Question 13

Percentile

Answer 13

often used when reporting data from normal distributions.

they represent the area under normal curve, increasing from left to right.

Question 14

what does a score in the 75th percentile indicate?

Answer 14

a score in the 75th percentile is higher than 75% of the rest of the scores.

see book page 301 for example.

Question 15

What does inferential statistics allow us to do?

Answer 15

inferential statistics allows inferences or assumptions to be made about data.

Question 16

what can we do with inferential statistics?

Answer 16

using inferential statistics such as a regression coefficient or a t-test, you can draw conclusions about the population you are studying. Inferential statistics starts with a hypothesis and checks to see if the data prove or disprove that hypothesis.

Question 17

variables

Answer 17

variables are the things that statistics is designed to test.

we check if an independent variable has an effect on the dependant variable.

Question 18

independent variable

Answer 18

an independent variable is the variable that is manipulated to determine what effect it will have on the dependent variable.

Question 19

dependent variable

Answer 19

a dependent variable is a function of the independent variable. As the independent variable changes, so does the dependent variable.

typically an independent variable is altered in a behavioral experiment and the dependent variable is the one measured.

Question 20

Common independent variables in behavioral sciences include :

Answer 20

age, sex, race, socioeconomic status, standardized measures and scores etc

Question 21

Sample size

Answer 21

sample size refers to the number of observations or individuals measured.

Typically denoted with N

Question 22

What does a larger sample size indicate?

Answer 22

increased accuracy

Question 23

statistical power

Answer 23

it is essentially the likelihood that you have enough subjects to accurately prove the hypothesis is true within an acceptable margin of error.

bigger sample sizes are always better. the larger the sample size, the more likely that you can draw accurate inferences about the population that the sample was drawn from.

Question 24

Random Samples

Answer 24

A random sample is a subset of individuals from within a statistical population that can be used to estimate characteristics of the whole population.

Question 25

What happens if the subset is not selected randomly?

Answer 25

if the subset is not selected randomly, then this non-randomness might unintentionally skew the results, which is called sampling bias.

Question 26

Two samples are considered to be significantly different is the p-value is below +-

Answer 26

0.05

Question 27

What if two data sets are determined to be statistically significantly different ( the p-value is below +- 0.05) ?

Answer 27

Then it can be concluded with 95% confidence that the two sets of data are actually different.

Question 28

Correlation

Answer 28

Expresses a relationship between two sets of data using a single number, the correlation coefficient ( usually represented as R of r)

a correlation coefficient can have a maximum value of +1 and minimum value of -1.

Question 29

Positive correlation

Answer 29

meaning a coefficient greater than zero

Indicates a positive association between the two variables, that is, when one variable increases, the other also tends to increase as well.

and vice versa - one decrease, the other also decrease.

Question 30

Negative Correlation

Answer 30

meaning a coefficient that is less than zero

when one increases, the other tends to decrease.

Question 31

What does a correlation coefficient of exactly 0 indicate?

Answer 31

It indicated that there is no linear relation between the two variables.

Question 32

does correlation imply causation?

Answer 32

NO

Question 33

Can we draw conclusions based on behavioral problems?

Answer 33

NO

the cream and new york murder rate correlation.

there is always a number of other factors that influence.

in the ice cream nurder example, a logical third factor might be temperature. as the temperature increases, so does the murder rate in new york city.

Question 34

Reliability

Answer 34

Reliability is the degree to which a specific assessment tool produces stable, consistent and replicable results.

The two types of reliability that you should be able to recognize on the exam are test-retest reliability and inter-rater reliability

Question 35

Test-retest reliability

Answer 35

is a measure of the reliability of an assessment tool in obtaining similar scores over time. In other words, if the same person takes the assessment 5 times, their scores should be roughly equal, not wildly different.

Question 36

Inter-rater reliability

Answer 36

Is a measure of the degree to which two different researchers or raters agree in their assessment.
For example, if two different researchers are collecting observational data, their judgements of the same person should be similar, not wildly different.

Question 37

Validity

Answer 37

Validity refers to how well an experiment measures what it is trying to measure.There are three important type of validity: internal, external and construct.

Question 38

Internal validity

Answer 38

refers to whether the results of the study properly demonstrate a casual relationship between the two variables tested.

highly controlled experiments (with random selection, reliable instruments etc. ) may be the only way to truly establish internal validity.

Question 39

What are confounding factors?

Answer 39

confounding factors are hidden variables ( those not directly tested for) that correlate in some way with the independent or dependent variable and have some sort of impact on the results.

Question 40

External validity

Answer 40

Refers to whether the results of the study can be generalized to other situations and other people.

Generalizability is limited to the independent variable.

These are the things that MUST be controlled :

• sample must be completely random
• all situational variables must be tightly controlled
• cause and effect relationships may not be generalizable to other settings, situations, groups, or people.

Question 41

Construct validity

Answer 41

is used to determine whether a tool is measuring what it is intended to measure. e.g.. does a survey ask questions clearly?

Question 42

`what happens in a Randomized controlled trial?

Answer 42

There are two groups, a treatment group and a control group.
The treatment group receives the treatment under investigation and the control group either receives no treatment, a placebo or ( the current standard care (this one is used mostly in most medical studies)

Question 43

What can answer questions about the effectiveness of different therapies or interventions?

Answer 43

Randomized controlled trials

Question 44

How does randomization helps?

Answer 44

Randomization helps avoid selecting a sample that is biased, and having a control group allows for a comparison.

Question 45

Double -blindedness

Answer 45

attempts to eliminate subjective, unrecognized biases held by the subjects and the researchers.

In a double blinded experiment, neither the participants nor the researchers know which participants belong to the control group, as opposed to the test group. After all the data has been recorded, the researchers learn which participants were which.

Question 46

What is a critical part of the double - blinded experiment?

Answer 46

Random assignment of test subjects to the experimental and control groups is a critical part of any double - blind research design.

Question 47

In which cases are the double- blind methods perfect?

Answer 47

Situation in which there is a possibility that the results will be affected by conscious/unconscious bias on the part of researchers, participants or both.