Chapter 5: Sampling and Probability

Question 1

Goal of most researchers

Answer 1

To collect data from a sample that represents the population

Question 2

Two main types of samples

Answer 2

Random samples and Convenient samples

Question 3

Random Sample

Answer 3

One in which every member of the population has an equal chance of being selected into the study

Question 4

Convenience Sample

Answer 4

One that uses participants who are readily available

Question 5

Generalizability

Answer 5

Can also be referred to as External validity; Refers to researchers’ ability to apply findings from one sample or in one context to other samples or contexts

Question 6

Replication

Answer 6

Refers to the duplication of scientific results, ideally in a different context or with a sample that has different characteristics

Question 7

Volunteer Sample

Answer 7

A special kind of convenience sample in which participants actively choose to participate in a study

Question 8

Problems with a Biased Sample

Answer 8

One person can never constitute a representative sample; it wouldn’t even make sense to calculate statistics on data from one person. This is a special kind of convenience sample a volunteer sample

Question 9

Random Assignment

Answer 9

Every participant has an equal chance of being assigned to any level of the independent variable;

Question 10

Random Selection

Answer 10

Almost never used; refers to a method of creating a sample from a population

Question 11

Random Assignment

Answer 11

Refers to a method we can use once we have a sample, whether or not the sample is randomly selected; more frequently used

Question 12

Confirmation Bias

Answer 12

Unintentional tendency to pay attention to evidence that confirms what we already believe and to ignore evidence that would disconfirm our beliefs

Question 13

Illusory Correlation

Answer 13

The phenomenon of believing one sees an association between variables when no such association exists

Question 14

Personal Probability

Answer 14

The likelihood of an even occurring based on an individual’s opinion or judgment; also called subjective probability; can also be called a guesstimate

Question 15

Probability

Answer 15

In statistics is the likelihood that a particular outcome will occur out of all possible outcomes

Question 16

Expected Relative-Frequency Probability

Answer 16

The likelihood of an event occurring based on the actual outcome of many, many trials

Question 17

Relative

Answer 17

Indicates that this number is relative to the overall number of trials

Question 18

Expected

Answer 18

Indicates that it’s what we would anticipate, which might be different from what actually occurs

Question 19

Trial

Answer 19

Refers to each occasion that a given procedure is carried out

Question 20

Outcome

Answer 20

Refers to the result of a trial

Question 21

Success

Answer 21

Refers to the outcome for which we are trying to determine the probability

Question 22

Formula for probability

Answer 22

probability = successes/trials

Question 23

Steps to calculate probability

Answer 23

1. Determine the total number of trials
2. Determine the number of these trials that are considered successful outcomes
3. Divide the number of successful outcomes by the number of trials

Question 24

The Law of Large Numbers

Answer 24

That probability only works only in the long run; in the long run, results are predictable

Question 25

Key factor in statistical probability

Answer 25

The individual trials must be independent

Question 26

Independent

Answer 26

In statistics, it means that the outcome of each trial must not depend in anyway on the outcome of previous trials

Question 27

Inferential Statistics

Answer 27

Hypothesis testing; helps to determine how likely a given outcome is

Question 28

Control Group

Answer 28

A level of the independent variable that does not receive the treatment of interest in a study

Question 29

Experimental Group

Answer 29

A level of the independent variable that receives the treatment or intervention of interest

Question 30

Hypothesis Compared in Inferential Statistics

Answer 30

Null Hypothesis and Research Hypothesis

Question 31

Null Hypothesis

Answer 31

A statement that postulates that there is no difference between populations or that the difference is in a direction opposite from that anticipated by the researcher; It proposes that nothing will happen

Question 32

Research Hypothesis

Answer 32

Alternative hypothesis; the exciting one; a statement that postulates that thee is a difference between populations or sometimes, more specifically, that there is a difference in a certain direction, positive or negative; proposes a distinctive difference that is worthy of further investigation

Question 33

Making a decision about the hypothesis

Answer 33

Decide to reject the null hypothesis

Decide to fail to reject the null hypothesis

Question 34

Two things that can be done after data is analyzed

Answer 34

Reject the null hypothesis; “I reject the idea that there is no mean difference between populations;”
Fail to reject the null hypothesis. “I do not reject the idea that there is no mean difference between populations.”

Question 35

Three rules of formal hypothesis testing

Answer 35

1. The null hypothesis is that there is no difference between groups, and usually our hypotheses explore the possibility of a mean difference
2. We either reject or fail to reject the null hypothesis. There are no other options
3. We never use the word accept in reference to formal hypothesis

Question 36

Two types of error using statistical language

Answer 36

Type I Errors and Type II Errors

Question 37

Type I Error

Answer 37

Occurs when we reject the null hypothesis, but the null hypothesis is correct; similar to a false-positive in a medical test

Question 38

Type II Error

Answer 38

Occurs when we fail to reject the null hypothesis, but the null hypothesis is false; like a false-negative in medical testing; indicates that we falsely failed to reject the null hypothesis; results in a failure to take action because a research intervention is not supported or in medical testing, a given diagnosis is not received.