C1 Intro to Probability and Data with R M1-3 Data

Question 1

Which type of variable is hdi (Human Development Index, combining factors of life expectancy, educational attainment, and income) with levels very high, high, medium, and low human development)?

Answer 1

Ordinal Categorical Variable

There is an inherent ordering to the levels of this categorical variable (from very high to low), and hence this is an ordinal categorical variable.

Question 2

What are the two main types of numerical variables?

Answer 2

Continuous and Discrete

Continuous variables can take any value within a range, while discrete variables can only take specific values.

Question 3

Define continuous variables.

Answer 3

Can take any value within a range (e.g., height)

Continuous variables allow for an infinite number of possible values.

Question 4

Define discrete variables.

Answer 4

Can only take specific values (e.g., number of cars owned)

Discrete variables are countable and often represented as whole numbers.

Question 5

What are the two categories of categorical variables?

Answer 5

Ordinal and Nominal

Categorical variables represent characteristics or qualities.

Question 6

Define ordinal variables.

Answer 6

Have a meaningful order (e.g., satisfaction levels)

The order matters in ordinal variables, unlike in nominal variables.

Question 7

Define nominal variables.

Answer 7

No inherent order (e.g., morning person vs. afternoon person)

Nominal variables categorize data without a ranking system.

Question 8

What do researchers do in observational studies?

Answer 8

Collect data without interfering with how it arises.

Question 9

What can researchers establish in observational studies?

Answer 9

An association (correlation) between variables.

In general, observational studies can provide evidence of a naturally
occurring association between variables, but they cannot by themselves show a causal connection.

Question 10

What are the two types of observational studies?

Answer 10

• Retrospective studies (using past data)
• Prospective studies (collecting data throughout the study)

Question 11

What is the main feature of experiments in research?

Answer 11

Researchers randomly assign subjects to treatments.

Question 12

What do experiments allow researchers to establish?

Answer 12

Causal connections.

Question 13

Why is random assignment important in experiments?

Answer 13

It helps control for confounding variables.

Question 14

What are confounding variables?

Answer 14

Extraneous factors that may influence both the explanatory and response variables.

Question 15

What is Convenience Sample Bias?

Answer 15

When only easily accessible individuals are included.

This type of bias can lead to non-representative samples because it does not account for the broader population.

Question 16

What causes Non-response Bias?

Answer 16

Occurs when a non-random fraction of the sampled individuals respond, leading to unrepresentative results.

It can skew the results if the non-respondents differ significantly from respondents.

Question 17

What is Voluntary Response Bias?

Answer 17

Arises when only those with strong opinions choose to respond.

This bias often leads to overrepresentation of extreme views in survey results.

Question 18

What is Simple Random Sampling?

Answer 18

Each case has an equal chance of selection.

This method ensures that every individual in the population has the same probability of being chosen.

Question 19

Define Stratified Sampling.

Answer 19

Population is divided into strata, and samples are taken from each.

This technique is useful for ensuring representation from different segments of the population.

Question 20

What characterizes Cluster Sampling?

Answer 20

Population is divided into clusters, and entire clusters are sampled.

This method is often used when populations are large and geographically dispersed.

Question 21

Explain Multistage Sampling.

Answer 21

Combines cluster sampling with additional sampling within selected clusters.

This approach allows for a more refined sampling process, potentially increasing efficiency.

Question 22

What is a strategy to minimize sampling bias in studies?

Answer 22

Use Random Sampling

Ensures that every individual in the population has an equal chance of being selected.

Question 23

What is Stratified Sampling?

Answer 23

Dividing the population into homogeneous subgroups and randomly sampling from each stratum

Ensures representation across key characteristics like age or gender.

Question 24

How does increasing sample size help in studies?

Answer 24

It reduces the impact of bias and increases the reliability of results

A larger sample size generally leads to more accurate and generalizable findings.

Question 25

What is a method to avoid sampling bias related to participant selection?

Answer 25

Avoid Convenience Sampling ## Footnote Relying solely on easily accessible individuals can lead to non-representative samples.

Question 26

What should be done to address Non-response Bias?

Answer 26

Follow up with individuals who do not respond to surveys ## Footnote Encouraging participation ensures a more representative sample.

Question 27

What is a benefit of using multiple sampling methods?

Answer 27

Enhances representativeness and reduces bias ## Footnote Combining methods like multistage sampling can improve the quality of the sample.

Question 28

What is the principle of Control in experimental design?

Answer 28

Comparing the treatment group to a control group. ## Footnote The control group serves as a baseline to evaluate the effect of the treatment.

Question 29

Define Randomization in the context of experimental design.

Answer 29

Randomly assigning subjects to different treatment groups. ## Footnote This helps to eliminate bias and ensures that the groups are comparable.

Question 30

What does Replication refer to in experimental studies?

Answer 30

Ensuring a sufficiently large sample size or repeating the entire study. ## Footnote Replication increases the reliability of the results.

Question 31

What is the purpose of Blocking in experimental design?

Answer 31

Grouping subjects based on known or suspected variables that may affect the response variable before random assignment. ## Footnote Blocking helps to control for variables that could confound the results.

Question 32

What is a placebo?

Answer 32

A fake treatment used as a control. ## Footnote Placebos are often used in clinical trials to test the efficacy of a new drug.

Question 33

What is the placebo effect?

Answer 33

Improvement due to belief in receiving treatment. ## Footnote This phenomenon can occur even when patients receive no active therapeutic intervention.

Question 34

What does blinding refer to in research?

Answer 34

Participants unaware of their group assignment. ## Footnote This helps reduce bias in the results.

Question 35

What is a double-blind study?

Answer 35

Both participants and researchers are unaware of group assignments. ## Footnote This design minimizes both participant and researcher bias.

Question 36

What is random sampling?

Answer 36

Selection of subjects randomly from a population, ensuring equal chance of being chosen ## Footnote This results in a representative sample that allows generalization of study results.

Question 37

What is the purpose of random sampling in study design?

Answer 37

To create a sample that is likely representative of the population ## Footnote This enables the results of the study to be generalized.

Question 38

What is random assignment?

Answer 38

Assignment of subjects to different treatment groups in experimental settings ## Footnote This ensures that differences in characteristics are equally represented in treatment and control groups.

Question 39

How does random assignment contribute to research?

Answer 39

It allows researchers to attribute observed differences in outcomes directly to the treatment being tested ## Footnote This strengthens the validity of causal conclusions.

Question 40

What are the implications of using both random sampling and random assignment in studies?

Answer 40

Allows for causal conclusions that can be generalized to the population ## Footnote Studies lacking one or both methods have limitations in their conclusions.

Question 41

True or False: Random sampling ensures that study results can be generalized to the population.

Answer 41

True ## Footnote A representative sample is essential for generalization.

Question 42

A study is designed to test the effect of light level and noise level on exam performance of students. The researcher also believes that light and noise levels might have different effects on males and females, so wants to make sure both genders are represented equally under different conditions. What would be the **explanatory, response and blocking variables** in this scenario?

Answer 42

The researchers are interested in the effect of light and noise on exam performance. Since they believe these two variables might be affecting the outcome, these are the explanatory variables and exam performance is the response variable. Gender of the student is a nuisance variable they want to control for, hence they block for it. Unlike light and noise, gender is not a treatment that is being imposed on the subjects.

Question 43

A retail store considering updates to their credit card policies randomly samples 1000 of their credit card holders to survey on the phone. The phone calls are made during business hours, therefore there is a lower rate of responses from members who work during these hours. What type of bias is this indicative of?

Answer 43

non-response bias ## Footnote There is an initial random sample, but not everyone in this random sample is reached. Therefore the issue is non-response of the sampled individuals.

Question 44

A city council has requested a household survey be conducted in a suburban area of their city. The area is broken into many distinct and unique neighborhoods, some including large homes, some with only apartments. Which approach would likely be the least effective?

Answer 44

The least effective approach would be *cluster sampling*, where each cluster is a neighborhood

Question 45

What is the most important difference between observational studies and experiments?

Answer 45

Random assignment ## Footnote Random assignment helps to eliminate bias and establish causality in experiments.

Question 46

What are associated variables?

Answer 46

When two variables show some connection with one another, they are called associated variables. Associated variables can also be called dependent variables and vice-versa. ## Footnote The multi-unit and home ownership rates are said to be associated because the plot shows a discernible pattern.

Question 47

True or False: A pair of variables is ASSOCIATED OR INDEPENDENT, NOT BOTH

Answer 47

A pair of variables are either related in some way (associated) or not (independent). No pair of variables is both associated and independent.

Question 48

When is said that a pair of variables are independent?

Answer 48

If two variables are not associated, then they are said to be independent. That is, two variables are independent if there is no evident relationship between the two.

Question 49

What is the term for a variable that might causally affect another?

Answer 49

Explanatory variable ## Footnote This variable is hypothesized to influence the response variable.

Question 50

What do we call the variable that is affected by the explanatory variable?

Answer 50

Response variable ## Footnote This variable responds to changes in the explanatory variable.

Question 51

Fill in the blank: The _______ variable is the one that might affect another variable.

Answer 51

explanatory ## Footnote This variable is often used in causal analysis.

Question 52

Fill in the blank: The _______ variable is the one that is affected by the explanatory variable.

Answer 52

response ## Footnote This variable measures the effect of the explanatory variable.

Question 53

What is stratified sampling?

Answer 53

A divide-and-conquer sampling strategy where the population is divided into groups called strata

Question 54

How are strata chosen in stratified sampling?

Answer 54

Strata are chosen so that similar cases are grouped together

Question 55

What is the second sampling method employed within each stratum in stratified sampling?

Answer 55

Usually simple random sampling

Question 56

Why is stratified sampling useful?

Answer 56

It is especially useful when the cases in each stratum are very similar with respect to the outcome of interest

Question 57

Fill in the blank: Stratified sampling is a _______ sampling strategy.

Answer 57

[divide-and-conquer]

Question 58

What are the four principles of experimental design?

Answer 58

Controlling, Randomization, Replication, Blocking

Question 59

What does controlling refer to in experimental design?

Answer 59

Researchers assign treatments to cases and control other differences in the groups

Question 60

What is the purpose of randomization in experiments?

Answer 60

To account for uncontrolled variables and prevent accidental bias

Question 61

Why is replication important in experimental design?

Answer 61

It allows researchers to estimate the effect of the explanatory variable more accurately

Question 62

What is blocking in the context of experimental design?

Answer 62

Grouping individuals based on a variable before randomizing them into treatment groups

Question 63

When is blocking particularly useful in an experiment?

Answer 63

When researchers suspect that other variables influence the response

Question 64

What is an example of using blocking in a drug study for heart attacks?

Answer 64

Split patients into low-risk and high-risk blocks before random assignment

Question 65

What is the significance of incorporating the first three principles of experimental design? | Controlling, Randomization & Replication

Answer 65

They are essential for any study to ensure valid results

Question 66

What does randomization help to prevent in a study?

Answer 66

Accidental bias

Question 67

Fill in the blanks An extraneous variable that is related to the explanatory and response variables and that prevents us from deducing causal relationships based on observational studies is called a _____

Answer 67

confounding variable

Question 68

In an experiment, what purpose does blocking serve?

Answer 68

Control for variables that may influence the response. If there are variables that are known or suspected to affect the response variable, we first group subjects into blocks based on these variables, and then randomize cases within each block to treatment groups. This allows us to control for possible effects of these confounding variables by making sure they are equally represented in all treatment groups.

Question 69

What is the purpose of random sampling in data collection?

Answer 69

To make results generalizable to the target population ## Footnote Random sampling ensures that every individual in the population has an equal chance of being selected, enhancing the representativeness of the sample.

Question 70

What does random assignment in study design suggest?

Answer 70

Causality ## Footnote Random assignment helps ensure that any differences observed in the study outcomes can be attributed to the treatment rather than pre-existing differences between groups.

Question 71

How does random sampling relate to the population?

Answer 71

It allows generalization of results to the population at large ## Footnote This is important for making valid inferences based on the sample studied.

Question 72

What type of sampling is described as stratified sampling?

Answer 72

Random sampling ## Footnote Stratified sampling involves dividing the population into subgroups and randomly sampling from each subgroup to ensure representation.

Question 73

Further classify a variable once it is identified as categorical.

Answer 73

If variable is categorical, determine if it is ordinal based on whether or not the levels have a natural ordering.

Question 74

Further classify a variable once it is identified as numerical.

Answer 74

If variable is numerical, further classify as continuous or discrete based on whether or not the variable can take on an infinite number of values or only non-negative whole numbers, respectively.

Question 75

True or False Labeling variables as explanatory and response does not guarantee that the relationship between the two is actually causal, even if there is an association identified between the two variables.

Answer 75

True