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Flashcards in CH 3 Deck (23):
1

Population mean

Find u = sum of population.

N = number of values in data set

Population mean = u/N

2

Median

Middle value WHEN numbers are arranged in ascending order.

3

Central tendency

Describes the average or typical data value.
Three measures = mean, median, mode

4

When data set is skewed

Median is preferred measure

5

When data set is not skewed

Mean is best

6

Standard deviation

s^2 = sum x^2 - (sum x)^2/n) / n-1

n = sample size

7

Dispersion

Degree to which the data are spread out.

8

Population standard deviation

o^2 = sum (x - u)^2 / N

u = population mean
N = observations in the population

9

Sample standard deviation

Take square root of sample variance.

10

Empirical rule

Histogram must be bell-shaped
- 68% of data lie within 1 standard deviation of the mean
- 95% lie within 2
- 99.7% lie within 3

11

Empirical rule calculation

x + s

12

Higher standard deviation is ___.

Riskier

13

Chebyshev's inequality

(1-1/k^2)100%

k = standard deviation

14

z-score

z = (x-u)/o

x = weight of baby born in week x
u = mean value
o = standard deviation

15

Quartile 2

Median of the data

16

Quartile 1

Median of the lower half of the data set.

17

Quartile 3

Median of the higher half of the data set

18

IQR

Interquartile range = Q3 - Q1

19

Lower fence

Are cutoffs for determining outliers:

Q1 - 1.5(IQR)

20

Upper fence

Q3 + 1.5(IQR)

21

A data point is considered an outlier IF

It is less than the lower fence or greater than the upper fence

22

5 number summary

= smallest and largest numbers in the data set, Q1, Median, and Q3

23

On a box plot..

Q1 = first black vertical line
Median = black line inside the box
Q3 = last vertical line