DECK 2

Question 1

What is a contingency table

Answer 1

shows distributions across 2 variables like gender acros music pref (male/female across hip hop/country/ classical). AKA 2-way table

Question 2

How can you tell if variables in a contingency table are independent?

Answer 2

If the distributions are the same across the variables.. Then it doesn’t DEPEND on which category it came from, it still has same likelihood as others….. it’s INDEPENDENT.

Question 3

marginal distribution

Answer 3

overall distributions of a single variable in contingency table (out in margins)

Question 4

conditional distribution?

Answer 4

A distribution within the table, along only one row or column on the inside of the table… NOT IN THE MARGINS

Question 5

Association and Independence?. How are they related?

Answer 5

Variables are either ASSOCIATED or INDEPENDENT. If they are associated, then they are not independent, if they are independent then they are not associated.

Question 6

mean/SD/median/IQR? what to use?

Answer 6

when unimodal and symmetric, us MEAN and SD. If skewed or outliers use Median and IQR. If BIMODAL Talk about the MODES and use range or IQR,

Question 7

How do you describe distributions (histograms)?

Answer 7

Shape-Cener-Spread-Outlierg-Gaps —- GSOCS? where’s yo GSOCS?

Question 8

If asked to compare distributions, what should you write about?

Answer 8

GSOCS.. Write a sentence comparing shapes, and then one comparing centers, then comparing spreads and finally gaps and outliers…

Question 9

Center description?

Answer 9

mean (balance), median (splits area in half), mode (peaks? if bimodal, talk about both modes) or ?. “centered around ____”

Question 10

Shape description?

Answer 10

unimodal, bimodal, multimodal, uniform, symmetric, skewed,

Question 11

Spread description?

Answer 11

We have many measures of spread: range, IQR, stand dev, variance, or simply say. From here to about here.

Question 12

what happens if you ADD a constant to each value in a data set?

Answer 12

it is SHIFTED only. This effects all of the data values and measures of center (mean, med) and quartiles, deciles, etc… IT DOES NOT CHANGE THE SPREAD!
(IQR, St Dev, Range all stay the SAME).

Question 13

what happens if you multiply all of a data set by a constant?

Answer 13

it is scaled.. Everything is effected. Mean/ median/ stand dev/ iqr/ quartiles all multiplied by that constant. Center, spread and all individual values are changed.

Question 14

What is the five number summary?

Answer 14

min, Q1, Q2(median), Q3 and max

Question 15

How do you find Q1 and Q3?

Answer 15

Q1 is the median of the bottom half (25th %ile) and Q3 is the median of the upper half (75th %ile)

Question 16

How can you match boxplots to histograms?

Answer 16

USE THE FISH TANK METHOD!

Question 17

For information purposes, which gives most? stem-leaf, histogram or box-whisker?

Answer 17

Stem leaf gives the actual values and the shape, histogram just the shape and box-whisker the least amt, but are great for comparing multiple distributions.

Question 18

What percent of the data is above Q3?

Answer 18

25%

Question 19

What percent of the data is below the median?

Answer 19

50%

Question 20

What percent of the data is between Q1 and Q3?

Answer 20

50%

Question 21

What is the IQR?

Answer 21

Interquartile range. a measure of spread.. Q3-Q1.. The distance from Q1 to Q3.

Question 22

What are the percentiles for Q1, med, and Q3?

Answer 22

25, 50 and 75

Question 23

where are the “outlier fences?”

Answer 23

1.5 IQR above Q3 and below Q1. Just a rule of thumb..

Question 24

How can you think of mean, median and mode to help understand?

Answer 24

Mean is balancing point of histogram, median splits area in half, mode is the peaks of histogram…

Question 25

What if mean median are way different?

Answer 25

There is evidence that the data is skewed or there is an outlier. (the mean chases the tail)

Question 26

Who is the best?

Answer 26

YOU ARE!! Because you are studying these here cards!!! Way to go. I am proud of you.