Statistic Final

population

entire collection of individuals about which information is sought

sample

subset of a population, containing the individuals that are actually observed

simple random sampling

a sampling method where every individual has an equal chance of being selected from the population

sample of convenience

a non-random sample taken from a population based on ease of access rather than random selection

stratified sampling

population is divided into groups where the members of each group are similar in some way- draw samples from each group

cluster sampling

a sampling method where the population is divided into clusters, and entire clusters are randomly selected for inclusion in the sample.

systematic sampling

a sampling method where members of the population are selected at regular intervals from a randomly ordered list.

voluntary response sampling

A sampling method where participants self-select to be part of the sample, often leading to bias as it may not represent the broader population.

statistic

number that describes a sample

parameter

number that describes a population

ordinal variables

qualitative variables whose categories have a natural ordering

nominal variables

qualitative varibales whose categories have no natural ordering

discrete variables

possible values can be listed

continuous variables

can take on any value in some interval

randomized experiments

experiments where participants are randomly assigned to different groups to test the effects of a variable.

double-blind experiments

experiments in which neither the participants nor the experimenters know who is receiving a particular treatment, helping to eliminate bias.

observational studies

the assignment to treatment groups is not made by the investigator

prospective studies

subjects are followed over time to identify how these factors affect the outcomes

cross-sectional studies

measurements are taken at one point in time

retrospective studies

subjects are sampled after the outcome have occurred

case-control studies

used to study rare diseases

voluntary response bias

occurs when individuals select themselves to participate in a survey, leading to unrepresentative samples.

self-interest bias

occurs when individuals' personal interests affect their responses, leading to skewed data.

social acceptability bias

occurs when respondents provide answers they believe are more socially acceptable rather than their true feelings or beliefs.

leading question bias

occurs when a question is phrased in a way that suggests a particular answer, influencing respondents' responses.

nonresponse bias

occurs when certain individuals do not respond to a survey or study, leading to a sample that may not represent the overall population.

sampling bias

some members are more likely to be included in the sample than others

Frequency Distributions for Data

how many observations in each category

Relative Frequency Distributions

tells us the proportion of observations in a category

empirical rule

68% of data will be within one standard deviation of the mean

95% within two standard deviations

all or almost all within three

Quartiles

1) arrange in increasing order

2) L1 = 0.25n

L2 = 0.75n

3) if L is a whole number, the quartile is the average of the number in position L and the number in position L+1. If L is not a whole number, round it up to the next high whole nnumber

probability

P(A) = number of outcomes in A/number of outcomes in the sample space

General Addition Rule

P (A or B) = P(A) + P(B) - P(A and B)

If A and B are mutually exlusive events, then

P (A or B) = P(A) + P(B)