Stats Exam 2

Question 1

What is a descriptive project

Answer 1

describes situation, not carry out hypothesis test

Question 2

what is a differences project

Answer 2

compares two sets of data, hypothesis relates to differences between two sets

Question 3

what is a correlation/regression project

Answer 3

emphasis on linking variables, looking at strength and direction of links between two or more variables

Question 4

what is an association project

Answer 4

looking for links between variables that are categorical

Question 5

what graph to use of a descriptive project

Answer 5

histograms, density plots, boxplots

Question 6

what graph to use for differences projects

Answer 6

bar charts and boxplots

Question 7

what graph to use for a correlation/regression project

Answer 7

scatterplots and line plots

Question 8

what graph to use for association projects

Answer 8

bar charts and pie charts

Question 9

What is the outcome of hypothesis testing

Answer 9

likelihood that a hypothesis is correct

Question 10

what do we test when we test a hypothesis

Answer 10

the null

Question 11

how does the p-value help make conclusions

Answer 11

tells the probability that the null hypothesis is correct

Question 12

what conclusions can we draw with a p-value

Answer 12

reject or fail to reject null hypothesis (no change/difference)

Question 13

code to make a histogram

Answer 13

hist(object)

Question 14

code to make a boxplot

Answer 14

boxplot(object)

Question 15

code to scale x axis

Answer 15

xlim=c(number,number)

Question 16

code to scale y axis

Answer 16

ylim=c(number, number)

Question 17

code to label x axis

Answer 17

xlab=”title”

Question 18

code to label y axis

Answer 18

ylab=”title”

Question 19

code to title graph

Answer 19

main=”title”

Question 20

code to change graph color

Answer 20

col=”color”, or col=c(“color 1”, “color 2”)

Question 21

what kind of test would be used for the alt hypothesis that “a cause has an effect” (not specified positive or negative)

Answer 21

two tailed t-test

Question 22

what kind of test would be used for the alt hypothesis that “a cause has a positive effect”

Answer 22

one tailed t-test

Question 23

what is popperian philosophy

Answer 23

one observation can disprove something but it takes an uncollectable amount of data to confirm something 100%

Question 24

what do frequent statistics measure

Answer 24

probability that a null hypothesis is incorrect

Question 25

what is the level of probability that scientists use for deciding what to do with hypotheses

Answer 25

0.05

Question 26

study setup that uses a t-test

Answer 26

finding the probability of drawing two samples with different means from a common population

Question 27

the increasing of what increases t

Answer 27

mean, standard deviation, number of replicates

Question 28

necessary to determine if a t-test can be used

Answer 28

Shapiro-Wilk test to determine if data is normal (must be greater than 0.05)

Question 29

r command from a t-test

Answer 29

t.test(object)

Question 30

what is the difference between 1 and 2 tailed t-tests

Answer 30

1 tailed specifies direction of change, 2 tailed does not specify direction, only that the means are different from the null

Question 31

when should paired t-tests be used

Answer 31

when sampling units are not independent and not randomly distributed. repeated observations collected for a single variable with two levels (fishing in the same spot on different days)

Question 32

how do non parametric tests work

Answer 32

ranking data

Question 33

r code for nonparametric test equivalent to 2 tailed t-test

Answer 33

wilcox.test(object, object)

Question 34

what is the nonparametric equivalent of a 2 tailed t-test

Answer 34

Mann-Whitney test

Question 35

what is the nonparametric equivalent of a paired t-test

Answer 35

Wilcoxon matched pairs test

Question 36

what is preliminary sampling

Answer 36

small study conducted to refine and evaluate sampling size, acceptability, and feasibility

Question 37

what is dummy data collection

Answer 37

use research and hypothetical data to decide on number of observations needed to detect and effect

Question 38

what is primary literature investigation

Answer 38

using previous research and data to learn about a system as much as possible and see how they can help your study design

Question 39

assumptions when using most stat tests

Answer 39

normality, equal variances, linearity, replicate independence

Question 40

pseudoreplication occurs when which statistical assumption is vilated

Answer 40

replicate independence

Question 41

what is pseudoreplication

Answer 41

if replicates are somehow tied together, not completely random

Question 42

what is simple pseudoreplication

Answer 42

only one replicate per treatment and subsamples are collected from each area and treated as replicates

Question 43

what is sacrificial pseudoreplication

Answer 43

experimental units are replicated and subsamples are treated as independent samples

Question 44

what is temporal pseudoreplication

Answer 44

single replicate per treatment and subsamples are collected from it repeatedly over time and treated as replicates

Question 45

what is phylogenetic pseudoreplication

Answer 45

closely related individuals are the units being sampled

Question 46

what is technical pseudoreplication

Answer 46

different observers or instruments are used for different parts of the experiment

Question 47

why must converting to categories must be done carefully

Answer 47

could create a misleading p-value

Question 48

what is a type 1 error

Answer 48

null is true but is rejected

Question 49

what is a type 2 error

Answer 49

null is false but not rejected