2 Data and Distributions

Question 1

What are the 2 types of studies

Answer 1

1. Observations studies

2. Experimental studies

Question 2

What is an observaitonal Study?

Answer 2

An observationsal study has no intervention by the researcher. Examples: surveys and polls

Question 3

What is an experimental study?

Answer 3

The researcher imposes treatements to observe changes in an experimental study. Example: plant growth trials.

Question 4

What studies can establish cause and effect?

Answer 4

Only experiments can establish cause and effect.

Question 5

What is a lurking variable?

Answer 5

A lurking variable is one that affects both variables.

When a lurking variable is present you cannot establish causation.

Question 6

What does it mean when a lurking variable is present?

Answer 6

When a lurking variable exists, there can be an association, but not a causation between two variables.

Question 7

What can estaiblish cause and effect?

Answer 7

Only a good experiment can establish cause and effect.

Question 8

What is an observational study?

Answer 8

An observational study involves observation only.

Question 9

What is an experimental study?

Answer 9

An experimental study imposes treatments on individuals to observe responses.

Question 10

What is a control group?

Answer 10

A control group is the group not receiving the treatment(s)

Question 11

What is a placebo?

Answer 11

A placebo is a fake treatment.

Question 12

What is a double blind experiment?

Answer 12

Neither the subject nor the people administering the treatments know who is receiving which treatment.

Question 13

What are the principles of good experimental design?

Answer 13

1. Randomisation
2. Control
3. Replication
4. Blocking

Question 14

What is randomisation in an experiment?

Answer 14

Randomly assign subjects to treatments.

Question 15

What is control in an experiment?

Answer 15

Control is a group not administered treatements. Control is necessary for the placebo effect another potential lurking variables.

Question 16

What is replication in an experiment?

Answer 16

Replication is achieved by having more than one subject or experiment or by repeating the whole experiment to reduce the impact of chance variation.

Question 17

What is blocking in an experiment?

Answer 17

Creating groups of similar cases in order to extract better information.

Question 18

What is CRD?

Answer 18

Completely randomised design. All subjects allocated at random to the treatment groups.

Question 19

What is a blok design?

Answer 19

IN a block design an SRS selected from each block in the population. A block is a similar group of cases.

Question 20

What is a matched pairs design?

Answer 20

A special type of block design where two treatments only are compared.

Question 21

Which 3 tupes of graphs can be used to display a quantitative variable?

Answer 21

1. Stem and Leaf Plot
2. Histogram
3. Boxplot

Question 22

What is an outlier?

Answer 22

An outlier is a value (or values) that is significantly removed from the main body of data.

Question 23

Which descriptions of centre and spread are best for a skewed distribution?

Answer 23

Skewed distribution - use measures that are not affected by outliers.
Centre = Median
Spread = IQR (interquartile range)

Question 24

Which measures are best for a reasonably symetric distribution?

Answer 24

Centre = mean
Spread = standard deviation