## Ch 1 Stats

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imaylenai  on September 13, 2008

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# Ch 1 Stats

 DataObservations (such as measurements, genders, survey responses) that have been collected.
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#### Definitions

Data Observations (such as measurements, genders, survey responses) that have been collected.
Statistics A collection of methods for planning studies and experiments, obtaining data, and then organizing, summarizing, presenting, analyzing, interpreting, and drawing conclusions based on the data.
Population The complete collection of all elements (scores, people, measurements, and so on) to be studied. The collection is complete in the sense that it includes all subjects to be studied.
Census Collection of data from every member of the population.
Sample A sub collection of members selected from a population.
Parameter Numerical measurement describing some characteristic of a population.
Statistic A numerical measurement describing some characteristic of a sample.
Quantitative data Consists of numbers representing counts or measurements. Describes a characteristic
Qualitative data Can be separated into different categories that are distinguished by some nonnumerical characteristic.
Discrete data When the number of possible values is either a finite number or a "countable" number. (That is, the number of possible values is 0 or 1 or 2 and so on.)
Continuous (numerical) data From infinitely many possible values that correspond to some continuous scale that covers a range of values without gaps, interruptions or jumps.
Ordinal level of measurement Catagories are ordered but differences are meaningless: 5 compact, 20 mid-size, 40 full-size cars
Interval level of measurement Differences are meaningful but there is no natural "0" starting point: Temperatures: 5, 10, 76
Ratio level of measurement There is a natural "0" starting point and ratios are meaningful: Student commuting Distance: 5mi, 20mi, 40mi
Voluntary response sample/Self-selected sample One is in which the respondents themselves decided whether to be included.
Observational study We observe and measure specific characteristics, but we don't attempt to modify the subjects being studied.
Experiment We apply some treatment and then proceed to observe its effects on the subjects.
Experimental units. Subjects in experiments are called?
Cross-sectional study Data are observed, measured, and collected at one point in time.
Retrospective study Data are collected from the past by going back in time (through examination of records, interviews, and so on).
Case-control Data are collected from the past by going back in time (through examination of records, interviews, and so on).
Prospective study/Longitudinal/Cohort Data are collected in the future from groups sharing common factors (called cohorts).
Confounding Occurs in an experiment when you are not able to distinguish among the effects of different factors.
Random sample Members from the population are selected in such a way that each individual member has an equal chance of being selected.
Simple random sample N subjects is selected in such a way that every possible sample of the same size has the same chance of being chosen.
Probability sample Involves selecting members from a population in such a way that each member has a known (but not necessarily the same) chance of being selected.
Systematic sampling Select a starting point and select every kth person i.e. every 50th person
Convenience sampling We simply use results that are very easy to get.
Cluster sampling Divide the pop. into sections and then randomly select certain sections and use all of the people in that section
Sampling error The difference between a sample result and the true population result; such an error results from chance sample fluctuations.
Nonsampling error Occurs when the sample data are incorrectly collected, recorded, or analyzed (such as by selecting a biased sample, using a defective measure instrument, or copying the data incorrectly).
Box Plot Min, Q1, Median, Q3, Max
Relative Frequency Part/Total
Usual Data Value Between x= -2s or x= +2s
Unusual Data Value Below x= -2s or above x= +2s
Which two data values are the only two to get rounded? Z-Scores and Median
Calculate class width Find the Range: Biggest # - Smallest # / The amount of classes wanted Round up
To find the mean, Variance, and SD on the Freq. Table Input the Freq. x Mid pnt. column and use the data from the calculator
Stratified Sampling Subdivide the population into groups that share a characteristic such as gender then draw a sample from each subgroup
Nominal Measurement Categories only with no ordering scheme: Student states: 5 Cali, 10 Texas

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