Midterm 1

Question 1

What are the four warnings in creating a histogram?

Answer 1

Choice of bin size has big affect
Changing axis range
Burying explanatory factors
How data is scaled

Question 2

How are strip charts better than histograms?

Answer 2

Better for comparing multiple data series

Question 3

What is the second step in sizing up data

Answer 3

Calculate Numerical descriptors
Mean
Median 
Mode
Quantiles 
Variance 
Standard deviation 
Min and max

Question 4

What are boxplots?

Answer 4

Graphical form of the quantiles

Question 5

What does the line inside a box in a boxplot represent?

Answer 5

Line indicates the median

Question 6

What does the box hold in a boxplot?

Answer 6

Box holds 50% of points

Question 7

What are the whiskers in a boxplot?

Answer 7

The whiskers hold remaining points

Question 8

What is a null hypothesis

Answer 8

Conservative statement saying that there isn’t an expected effect

Question 9

What is a p-value

Answer 9

A measure of the strength of the evidence against a null hypothesis

Question 10

How do we find the confidence level?

Answer 10

(1-p) x 100

Question 11

What is sums of squares and how is it measured?

Answer 11

SSY is how we measure variability

Sum of each value minus grand mean squared

Question 12

What is the relationship between SSY and n

Answer 12

SSY always increases with n

Question 13

How to find variance

Answer 13

SSY/ n-1

Question 14

what is the equation for standard variation

Answer 14

Square root of variance

Question 15

What are the three variability arising in a data set?

Answer 15

Variability of the population (sigma)?
Variability by the sample (s)
Variability of the estimated mean

Question 16

Why is standard error of the mean important

Answer 16

SEM can give us confidence intervals for our estimate of the population mean

Question 17

How to find confidence intervals

Answer 17

Mean-tcrit (SD/ square root of sample size)

Question 18

Relationship between estimate range and confidence level

Answer 18

A wider estimate range gives you a high confidence level

Question 19

What is ANOVA

Answer 19

Analyze the difference among group means. Compare differences in values between treatments to the variation within a treatment group

Question 20

What is the response variable

Answer 20

A continuous variable that is being influenced

Question 21

What is a explanatory variable

Answer 21

Categorical or continuous variable that influences

Question 22

In ANOVA, how do you find the total mean square

Answer 22

SSY/ df

Question 23

What is linear regression

Answer 23

Can the value of he response variable(x) be predicted by the explanatory variable

Question 24

Differences between ANOVA and regression?

Answer 24

ANOVA: discrete x values, values are names, values are unordered
Regression: continuously varying, values have number meaning, values are ordered

Question 25

What is statistical elimination?

Answer 25

Including the second extra lavatory variable allowed us to eliminate its influence in the rest of our model

Question 26

What are the four principles of experimental design?

Answer 26

Replication Randomization Blocking Orthonogonality

Question 27

What is replication

Answer 27

Multiple measures of the same thing Appears in the # of error degrees of freedom(residuals) Have at least 10 df for error

Question 28

What is randomization

Answer 28

Treatments need to be applied to experimental units randomly Use uniformly distributed random numbers

Question 29

What cardinals sins does randomization avoid

Answer 29

Systemic design: similarity between plots that undermines replication Unconscious bias in assigning treatment groups Using haphazard bs random design

Question 30

What is blocking?

Answer 30

Tool to minimize error variation Distribute individual data points into different "blocks" yo minimize biases due to known common features of subsets of the points Acts as another explanatory variable

Question 31

What are the rules for block design

Answer 31

Blocks used to account for a factor that could influence response Blocks should be used as internally homogeneous as possible If possible, all treatments should be included in all blocks

Question 32

What is Latin square design

Answer 32

2 way blocking. Blocking so that each treatment appears exactly once in each row and column:

Question 33

What is orthogonality

Answer 33

The acknowledgement that one variable tell you nothing about the other variable

Question 34

What is the benefit of orthogonal design

Answer 34

There is no statistical elimination between orthogonal explanatory variables

Question 35

Which variables are easier for orthogonality

Answer 35

Easier for categorical variable than continuous variables

Question 36

What is the first step in sizing up data?

Answer 36

Make a graph

Question 37

In continuous explanatory variables what do the p-values in ANOVA table represent?

Answer 37

That each explanatory variable has no influence on the response variables

Question 38

With continuous variables, what do the p-values represent in the coefficients table

Answer 38

That each specific coefficient value equals zero

Question 39

In a continuous variable, what does the p-value mean overall?

Answer 39

Neither explanatory variables can be used to predict the response variable

Question 40

In a categorical variable, what does the p-value mean in the ANOVA table?

Answer 40

That each explanatory variable has no influence in the response variable

Question 41

In a categorical variable what does the p-value mean in the coefficients table mean?

Answer 41

Each specific coefficient value equals 0

Question 42

In a categorical variable, what does the overall p-value mean in the coefficients table?

Answer 42

That neither of the variables can be used to predict the response variable

Question 43

How does blocking affect residuals?

Answer 43

Blocking helps by reducing the size of the residuals. Increasing F but lowering P

Question 44

What is an interaction

Answer 44

Two x-variables interact of the effect of one x-variable on y depends on the level of the other

Question 45

Regarding interactions, what does non-parallel lines indicate

Answer 45

There is an interaction

Question 46

Regarding interactions, what does two parallel line indicate?

Answer 46

There are no interactions

Question 47

In which case are r-squared values high and low with and without interactions

Answer 47

Model without interactions have a low r- squared value while model with interactions have a higher-squared values