Chap 3: Numerical descriptive measures Flashcards Preview

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Flashcards in Chap 3: Numerical descriptive measures Deck (19):
1

central tendency?

numerical variables are grouped around a typical, central value
Ex: mean, median, mode

2

variation?

show the amount of dispersion, scattering away from a central value
Ex: range, variance, Std dev, coefficient of variance, Z-score

3

shape?

the pattern of the distribution
from lowest -> highest
Ex: skewness & Kurtosis

4

the mean?

= balance point

5

median?

middle value in an ordered array of data ranked from smallest -> largest
= (n+1)/2 ranked value
Ex: median num of calories = 110 ---> half of breakfast cereals have equal or less than 110 calories

6

rules to determine median?

1. odd num of values -> median = middle ranked value
2. even num of values -> average of the two middle-ranked values

7

mode?

values appear most frequently

8

range

= diff btw largest n smallest value
= total spread of data

9

variance n Std Dev

how large values fluctuate above/below the mean
never be negative
Ex: Std Dev = 46.09 ---> the calories are clustering within +/- 46.09 around the mean 15.

10

coefficient of variation

- measures the scatter of data relative to mean
- always in %
- useful when comparing 2 data sets

11

Z scores

help identify outliers
> 3 and outlier

12

skewness?

measure the extent to which data values are not symmetrical around the mean

13

perfectly symmetrical?

skewness = 0

14

mean

negative, left skewed distribution

15

mean = median

symmetrical distribution w zero skewness

16

mean > median

positive, right skewed distribution

17

5 number summary

Xsmallest, Q1, median, Q3, Xlargest
Q1=(n+1)/4 ranked value
Q3 (3x(n+1))/4 ranked value

18

left skewed?

distance Xsmallest -> med GREATER median -> Xlargest
Xsmallest -> Q1 GREATER Q3 -> Xlargest
Q1 -> med

19

Covariance?

measure the strength of the linear relationship btw 2 numerical variables (X n Y)