Exam 1 Glossary R

# Exam 1 Glossary R - Glossary for terms on Exam 1 bar graph...

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Glossary for terms on Exam 1 bar graph: a graphical representation of categorical data. Names of each category are listed on the x axis and a bar is place over each category name having height equal to the frequency (or percentage) in that category. bias : A condition that occurs when the design of a study systematically favors certain outcomes. blocking: The grouping of individuals according to some characteristic like rats in the same litter or plots of land at the same location. The random allocation is carried out separately within each group. boxplot: A plot of data based on the five number summary. A line is drawn from the minimum observation to Q1; a box is drawn from Q1 to Q3 with a vertical line at the median and a line is drawn from Q3 to the maximum observation. categorical variable: A variable that can be classified into groups or categories such as gender, religion, zip-code, etc. Typically, words are used to describe an individual. comparative study: A study where the explanatory variable has two active treatments rather than an active treatment versus a control. Purpose of study is to determine which treatment works best rather than whether a treatment works. Randomization together with comparison enables the researcher to control lurking variables and apply the laws of probability for inference. completely randomized design: An experimental design where all individuals participating in the experiment are assigned at random to the treatments. confounded variable: A variable whose effect on the response variable cannot be separated from the effect of the explanatory variable on the response variable. (Note: Usually confounded variables are lurking variables but only a few lurking variables are also confounded.) confounding : A situation where the effect of one variable on the response variable cannot be separated from the effect of another variable on the response variable. control : An ‘inactive’ treatment where no experimental condition is applied to the individuals in order to determine whether the active treatment works. Randomizing together with a control enables the researcher to manage lurking variables when there is not a comparison group. Note: a control is not necessary for a valid experiment as long as two or more comparison treatments are used. convenience sample: A sample where the researcher contacts those subjects who are readily available and does not use any random selection. The results are almost surely biased. distribution:

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Exam 1 Glossary R - Glossary for terms on Exam 1 bar graph...

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