Stats 210 Exam 1

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Statistics

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Science that involves the extraction of information from numerical data obtained during an experiment or from a sample.

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Population

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The entire group of individuals (subjects) about which the researcher wants information

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Parameter

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Some characteristic of the population that the researcher wants to measure

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Sample

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A subset of the population that we examine in order to gather information

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Statistic

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A descriptive measure, usually computed from a sample, which can be expressed or evaluated numerically

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Inference

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A statement about a population based on the data collected in a sample

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Distribution

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A listing of all the possible values that a characteristic can take and the number (or percentage) of times that each value occurs

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Descriptive statistics

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The branch of statistics concerned with numerical and graphical techniques for describing one more characteristics of a population and for comparing characteristics among populations

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Qualitative (or categorical) variable

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Variable whose measurements vary in kind or name but not in degree, meaning that they cannot be arranged in order of magnitude

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Quantitative variable

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The variable whose measurements vary in magnitude from trial to trial, meaning some order or ranking can be applied

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Discrete quantitative variable

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A variable whose measurements can assume only a countable number of possible values

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Continuous quantitative variable

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Variable whose measurements can assume anyone of a countless number of values in a line interval

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Selection Bias

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exists when one or more types of subjects are systematically excluded from the sample

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Non-response bias

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exists when individuals chosen for the sample cannot be contacted or fail (or refuse) to respond

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Response bias

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exists when the respondents give inaccurate information (especially on questions that involve legal or social behavior issues) or if the interviewer influences the subject to respond in a certain way due to the wording of the question

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Haphazard sample

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involves selecting a sample by some convenient mechanism that does not involve randomization

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Volunteer response sample

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exists when people volunteer to be part of a study

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simple random sampling

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exists when we attempt to make a list of all possible individuals in the population and randomly choose n of the subjects in such a way that every set of n subjects has an equal chance to be in the sample (n is the sample size)

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stratified random sampling

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the population is naturally divided into two or more groups of similar subjects (strata) and a representative number of subjects are selected from each strata

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multistage random sampling

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the population is divided into groups of individuals and simple random sampling is used to randomly select some of these groups

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experimental units

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the subjects (individuals, units) on which the measurements are made

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treatment

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a specific experimental condition applied to the experimental units

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response

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the characteristic that is measured on each experimental unit that the experimenter wants to evaluate

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comparison

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all experiments must involve ________ of the responses among two or more groups

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Treatments Groups

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The group or groups of experimental units who receive a treatment

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Control Group

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A group of experimental units who do not receive one of the treatments

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Placebo

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A fake treatment that is given to the experimental units in the control group which (hopefully) prevents them from knowing if the received the treatment or not

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Replication

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repetition of the experiment on many experimental units in each group, which should reduce chance variation in the results

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Randomization

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The use of impersonal chance to assign experimental units to the groups

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Blinding

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The experimental units should not know to which group they have been assigned

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Double-blinding

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In addition to the experimental units not knowing to which group they have been assigned, those people who have contact with the experimental units also should not know to which group the experimental units have been assigned

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Bias

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anything, such as a factor not considered, that systematically favors certain outcomes over others and which causes the experimenter to question the validity of the results

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confounding

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the existence of some factor other than the treatment that makes the treatment and control groups different

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controlled experiment

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a designed procedure in which we randomly select experimental units to be in the experiment and can control which are assigned to the treatment group(s) and which are assigned to the control group

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Observational study

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A procedure in which we cannot (or do not) control which experimental units are assigned to the groups and hence only observe anecdotal evident