Exam 1 Flashcards by Samantha Boyer

parameter

characteristic of a population

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statistic

characteristic of a sample

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descriptive statistics

collection, organization, summarization, presentation of data

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inferential statistics

generalizing from samples to populations, estimatinons, hypothesis testing, determining relationships, making predictions

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inferential stats based on _________

probability

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qualitative

variables can be placed into distinct categories according to some characteristic

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quantitative

variables are numerical and can be ordered/ranked

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2 types of quantitative data

discrete
continuous

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nominal data

mutually exclusive, exhausting categories which cannot be ordered/ranked

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ordinal data

categories with no precise differences which can be ranked

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interval data

data is ranked and precise differences exist, but there is no meaningful 0, so ratios are meaningless

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ratio data

data is ranked and precise differences exist, and ratios are meaningful because there is a meaningful 0

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systematic sampling

every kth subject

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stratified sampling

divide population into layers and sample from each

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cluster sampling

sample from existing groups

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sample population

portion of target population accessible for sampling from

we take the sample from the sample pop.

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problem with simple random sampling

can give a nonrepresentative sample

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2 stages of cluster sampling

randomly select clusters
from clusters, randomly select subjects

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3 nonsampling errors

nonresponse
response error
selection bias

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frequency distribution

organization of raw data in table form, using classes as frequencies

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categorical distribution is for … data

nominal

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grouped distribution is for…. data

data with a large range requiring classes several units in width

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ungrouped distribution is for …. data

numerical data with a small range

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steps for constructing a frequency distribution

make categories
count/tally
find frequency
find relative frequency

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relative frequency =

frequency / total

all categorical data can be represented by a ....

bar graph

class boundaries

used to separate classes | ****

class rules

1. **limits** should have same decimal place value as data 2. **boundaries** should have one additional place and end in 5 3. width must be the **same** for every class 4. width should be an **odd** number 5. there should be **5-20** classes 6. classes should be **exhaustive, mututally exclusive, continuous**

class width =

range / # of classes

find class midpoint by...

taking avg of 2 class boundaries

steps to construct a grouped distribution

1. determine classes and class width 2. sort data into classes 3. find frequencies 4. find cumulative frequencies

uses class bounderies (x ax) and frequencies (y ax) to give a "bar graph" with bars that cannot be rearranged

histogram

uses lines to connect points plotted at the midpoint of each class

polygon

a polygon is anchored...

at the x ax before and after the data

uses lines that connect points plotted at the cumulative frequency of each class

ogive

an ogive has.... on the x ax

upper class boundaries

graph using proportions

relative frequency graph

used for categorical variables; bars arranged highest to lowest

Pareto chart

represents data that occur over a period of time

time series graph

bell shape

uniform shape

right skewed shape

left skewed shape

bimodal shape

weighted mean formula

table for grouped data's mean mean formula

A: class B: frequency, f C: midpoint, Xm D: f(Xm) mean = ΣD/n

mean for grouped data is ......

approximate

find median for an odd n

(n + 1)/2

find median for an even n

find mean of n/2 and (n+1)/2

measures of central tendency for right skew

mode < median < mean

measures of central tendency for left skew

mean < median < mode

variance

average deviation squared

s^2

sample variance

standard deviation

square root of variance

variance and std dev used to determine ...... of a variable

consistency

steps to find std dev

1. find mean 2. find deviation of each value: x - mean 3. square each deviation 4. find sum of the squares 5. divide by N or n-1

standard deviation =

unbiased estimate is ....... and is used to...

n - 1 compensate for the underestimation of population variance given by n alone

coefficient of variation =

100 (s/x)

range rule of thumb

s = R/4

range rule of thumb works when...

data is unimodal and approximately symmetric

chebyshev's formula

chebyshev's theorem states...

proportion of values from a data set that fall within k standard deviations of the mean will be at least 1 - 1/k^2 where k > 1

% for k = 2

75%

% for k = 3

88.9%

% for k = 4

93.8%

empirical rule applies to ..... distributions

normal

empirical rule 1 s: 2 s: 3 s:

1 s: 68% inside, 16% on either side 2 s: 95% inside, 2.5% on either side 3 s: 99.7% inside, 0.15% on either side

standard/z score definition

unitless measure expressing how many s above or below the mean an observation is

z score used when...

raw data can't be directly compared

z =

percentiles used in...

education, healthcare

percentile indicates...

position of an individual in a group

P is... such that....

P is an integer between 1 and 99 such that the Pth percentile is a value where P% of the data is less than or equal to the value

percentile =

[(values below x) + 0.5 / total # of values ]100

the cth value corresponds to the Pth percentile formula

c = nP/100

if c is a decimal...

round up

if c is a whole....

take avg of cth and (c+1)th values

Q1 = __th percentile

25th

Q3 = __th percentile

75th

steps to find quartiles

1. arrange data in order 2. find median, Q2 3. Q1 = median of first half 4. Q3 = median of second half

5-number summary

min max Q1 median Q3

hypothesis testing

decision-making process for evaluating claims about a population, based on information from samples

how to find outlier interval

Q1 - IQR(1.5) and Q3 + IQR(1.5)

5 number summary

min Q1 median Q3 max