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