Term | Definition |
Variable | a characteristic or attribute that can assume different |
Data | the values the variables assume |
Random Variable | variables whose values are determined by chance |
Data Set | a collection of data values |
Data Value - Datum | each value of the data set |
Probability | the chance of an event occurring |
Population | all the subjects that are being studied |
Sample | a group of subjects selected from a population |
Hypothesis Testing | decision-making process for evalutating claims about a population |
Statisitics | the science of conducting studies to collect, organize, summarize, analyze, and draw conclusions from data |
3 examples of how statistics is used in everyday life | gambling, sports, public health |
3 reasons to study statistics | Read and understand the various statistical studies performed in your fields
You may be called on to conduct research in your field
Can become better consumers and citizens |
Descriptive | consists of collection, organization, summarization, and presentation of data Ex. U.S. population senses |
Inferential | generalizing from samples to populations, performing estimations and hypothesis tests, determining relationships among variables, and making predictions. Ex. gambling |
Quantitative | numerical and can be ordered or ranked Ex. age, height, weight |
Qualitative | can be placed into distinct categories but not ranked Ex. gender, color, religion |
Discrete | quantitative- variables that assume values that can be counted Ex. # of children, # of students |
Continuous | quantitative- variables that can assume an infinite number values between any 2 specific values. Ex. capacity |
Boundaries | Ex. 18 17.5 - 18.5
4.68 4.675 - 4.685 |
Nominal | no order or rank can be imposed on the data Ex. gender, zip code |
Ordinal | precise differences between ranks do not exist Ex. rating public speakers, rating floats (1st, 2nd, 3rd) |
Interval | precise differences between units of measure; no meaningful zero Ex. IQ test, Temperature |
Ratio | same as interval but with a meaningful zero Ex. height, weight |
2 purposes of data collection | to describe situations or events
to help people make better decisions before acting |
3 ways to collect data | surveys, survey records, direct observation |
Random Sampling | putting random numbers in a hat and having people pull them out randomly |
Systematic Sampling | every fourth person being selected from a group |
Stratified Sampling | splitting people into groups by gender and only taking 10 from each group |
Cluster Sampling | characterizing people into 5 groups and taking all the people of 2 of these groups |
Telephone survey | advantage-people can be more candid
disadvantage- not all people can be surveyed |
Mailed survey | advantage- can cover a wider geographic area
disadvantage- low number of responses |
Personal interview | advantage- can obtain in-depth response
disadvantage- more costly |
Observational- Examples | Age of motorcycle owners |
Experimental- Examples | Type of instruction affects the number of sit-ups |
Observational- advantages and disadvantages | Natural setting; can be done in dangerous situations; can be done using variable that can't be manipulated
Definite cause and effect can't be found; expensive and time consuming; may have inaccuracies in measurements |
Experimental- advantages and disadvantages | Researcher can decide how to select and group subjects; can control the manipulated variable
Unnatural setting; Hawthorne Effect; Confounding variable |
Independent Variables | the variable that is being manipulated by the researcher |
Dependent Variables | the variable that is being studied to see if it changes due to the manipulated |
5 uses of statistics | To describe data; To compare two or more data sets; To determine if variables are related; To test hypothesis; To make estimates about population variances |
7 misuses of statistics | Suspect samples; Ambiguous averages; Changing the subject; Detached statistics; Implied connections; Misleading graph; Faulty survey |
Things that make bad questions | Biased questions; Confusing words; Double-barreled questions; Double negatives in a question; Improper ordering of questions |
Problems of getting random samples and systematic | being able to number the whole population |
true vs. quasi experiments | True- sample selected randomly
Quasi- using intact group because separation is not possible |
Confounding Varibles | a variable that influences the results of dependent but cannot be separated from the independent |
Hawthorne Effect | the subject knows that they are participating and purposely change their behavior in ways that it affects the results |
Control Group | the group that does not receive the treatment |
Treatment group | the group that receives specific treatment |
Margin of Error | +/- 1/(sq rt n) |
MoE Interval | The percent +/- the margin of error |
Biased question | a question that leads people to respond a certain way changing the results of the study |
Sequential Sampling | used in quality control |
Double sampling | Giving a huge population a questionnaire to find out who is qualified for the actual study |
Multistage sampling | uses multiple types sampling |