Statistics II

Question 1

What does ANOVA stand for?

Answer 1

Analysis of Variance

Question 2

What are ANOVA models?

Answer 2

Statistical models used to analyze the differences between group means and their associated procedures (such as “variation” among and between groups).

Question 3

What does ANOVA provide in its simplest form?

Answer 3

ANOVA provides a statistical test of weather or not the means of several groups are equal, and therefore generalizes t-test to more than two groups.

Question 4

Why should a t-test not be used, if there are more than two groups?

Answer 4

Doing multiple two-sample t-tests would result in an increased chance of committing a type I error.

Question 5

What does MANOVA stand for?

Answer 5

Multivariate Analysis of Variance

Question 6

When is MANOVA used instead of ANOVA?

Answer 6

It is used when there are two or more dependent variables.

Question 7

What questions can MANOVA help to answer?

Answer 7

1. Do changes in the independent variable(s) have significant effects on the dependent variables?
2. What are the interactions among the dependent variables?
3. What are the interactions among the independent variables?

Question 8

What does MANCOVA stand for?

Answer 8

Multivariate Analysis of Covariance

Question 9

What does it mean to have a problem with an unbalanced design in an ANOVA test?

Answer 9

the groups are of different sizes

Question 10

What is a fixed factor?

Answer 10

A factor only occurring in previously fixed values.
e.g. medicine (1, 2, 3)
species (raven, crow)

Question 11

What is a random factor?

Answer 11

randomly selected values out of a population of values

Question 12

When repeating an experiment, what factors would have the same values?

Answer 12

the fixed factors

Question 13

What does “Paired Comparison” mean?

Answer 13

before/after - design
both measurements must be taken from the same subject
e.g. blood pressure before and after training
behavior in environment A and environment B

Question 14

What does it mean to have “Repeated Measures”?

Answer 14

several effects on each subjects

e.g. several drugs on each subject

Question 15

What are the advantages of “paired comparison” and “repeated measurement” designs?

Answer 15

Variance between individuals can be ignored.

Smaller effects can be measured, which would usually be cancelled out by inter-subject variance.

Question 16

Explain the following abbreviation in paired comparisons:
Xi1
Xi2
Di

Answer 16

Xi1 … value for individual i before
Xi2 … value for individual i after
Di = Xi1 - Xi2 … difference for individual i

Question 17

Basic branches of applied statistics:

Answer 17

descriptive statistics 
inferential statistics (hypothesis testing, confirmatory ... )
exploratory analysis, modeling, data mining

Question 18

Why is it called inferential statistics?

Answer 18

Inferences on the whole population are drawn from sample.

Question 19

Examples of common quantiles?

Answer 19

median
upper quartile
lower quartile
deciles
percentiles

Question 20

“Bad” data can usually be classified as either
… or
…

Answer 20

incomplete or

incorrect

Question 21

List two potentially serious weaknesses of discarding incomplete records in a data set!

Answer 21

1) possibility of selection bias distortions

2) dramatic reduction in the size of data set

Question 22

Two ways of handling missing data:

Answer 22

1) discard incomplete records

2) insert substitute values

Question 23

One problem with using substituted values for incomplete data:

Answer 23

Essentially we would be making up data.

Question 24

An outlier is …

Answer 24

… a value that is very different from the others, or from what is expected.

Question 25

Difference between experimental and observational studies (and data)?

Answer 25

In experimental studies objects are manipulated (e.g. subjects taking different amounts of a drug).
In observational studies data is just recorded (e.g. telephone surveys, data about distant galaxies).

Question 26

What does it mean if the allocation of subjects to test groups is “double blind”?

Answer 26

During the experiment neither subject nor experimenter know in which group the subject is in.

Question 27

An experiment with two conditions can be regarded as a …

Answer 27

… simple two-group experiment.