Distributions and Histograms

Question 1

Visually representing continuous variables

Answer 1

Histogram (predictor variable is cont.); column chart with bins and no categories; count # of values greater than min. up to but not including max.

Question 2

Bar height

Answer 2

of observations in bin

Question 3

Bar width

Answer 3

Range of values of the continuous variable

Question 4

Patterns of distributions

Answer 4

Bell-shaped/normal, U-shaped, Right-skewed/positive, Left-skewed/negative

Question 5

Bell-Shaped/Normal:

Answer 5

Symmetric/unimodal
Skewness value of 0
Many naturally occurring characteristics are normally distributed

Question 6

U-Shaped:

Answer 6

Symmetric, bimodal (two distributions)

Question 7

Right-skewed/Positive:

Answer 7

Long right tail
Skew=running into a max. or min. possible value; could have min. and no max. or opposite
Asymmetry

Question 8

Left-skewed/Negative:

Answer 8

Long left tail
Skew=outliers
Mean is influenced by outliers
Asymmetry

Question 9

Describing distributions with descriptive statistics

Answer 9

Central tendency, variability

Question 10

Central Tendency

Answer 10

mean (average/normal), median (middle value/skewed), mode (most frequent value/bimodal)

Question 11

Variability

Answer 11

Standard deviation (normal), interquartile range (skewed), range (high-low)

Question 12

Standard Deviation

Answer 12

Shows how closely points cluster around the mean; “average” amount the points deviate, or differ, from the mean

Question 13

Median

Answer 13

Found by calculating middle of minimum and maximum values then averaging those values; less sensitive to outliers or skew

Question 14

IQR

Answer 14

Quartiles are values that cut the distribution in quarters; IQR= Q3-Q1

Question 15

Box and Whisker Plot

Answer 15

Box plots represent the min, Q1, median, Q3, and max; outliers are black dots on whiskers

Question 16

Main Effects

Answer 16

1 outcome and certain # of predictors

Question 17

Associated (related):

Answer 17

Outcome is diff. by levels of predictor

Question 18

Independent (not related):

Answer 18

Outcome is same by levels of predictor

Question 19

Interaction:

Answer 19

Effect of one predictor is different depending on level of other predictors

Question 20

Additive:

Answer 20

Effect of one predictor is same regardless of level of other predictors

Question 21

Effect Size

Answer 21

The magnitude (strength) of the association between predictor and outcome; based on difference between means and variability

Question 22

Effect Size and Mean Differences

Answer 22

If variability is same, but one pair of means are farther apart then there is less overlap, bigger effect size, and easier to detect

Question 23

Effect Size and Variability

Answer 23

If mean differences are the same, but one pair has smaller variability then there is less overlap, bigger effect size, and easier to detect

Question 24

Ceiling effect/Floor effect

Answer 24

Runs into upper/lower limit

Question 25

Converting continuous values into categories

Answer 25

Count frequency of each category and create column chart