| A | B |
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| Statistics | collection of methods for planning experiments, obtaining data, ect. and drawing conclusions based on the data. |
| popualtion | the complete collection of all elements to be studied. |
| census | the collection of data from every element in a population. |
| sample | a subcollection of elements drawn from a population |
| parameter | a numerical measurement describing some characteristic of a population |
| statstic | a numerical measurement describing some characteristic of a sample |
| Quantitative data | consist of numbers representing counts or measurements |
| Qualitative data | can be seperated into different categories that are distinguished by some nonnumeric characteristic |
| discrete data | result when the number of possible values is either a finite number or a countable number. (0, 1, or 2 and so on) |
| continuous data | result from infinitely many possible values without gaps, interruptions, or jumps. |
| nominal level of measurement | characterized by data that consist of names, labels or categories only, data can't be arranged low to high |
| ordinal level of measurement | can be arranged in some order, but differences between data values either can't be determined or are meaningless. Ex. Course grades A, B, there is an ordering but A can't be - from B. |
| interval level of measurement | is like ordinal with the additional property that the difference between any 2 data values is meaningful. However there is no natural 0 starting point. Ex. temp., years |
| ratio level of measurement | the interval level modified to include the natural 0 starting point. Zero indicates that none of the quanity is present. |
| self-selected survey | is when the respondents themselves decide whether to be included |
| Loaded questions | survey questions worded to get a desired response |
| misleading graphs | pie charts and bar graphs are visual devices used to exagerate or diminish the true data |
| precise numbers | when a statement includes a very precise figure- many people believe that just because it is precise it is accurate |
| Observational study | observe & measure specific characteristics, but we don't attempt to modify the subjects being studied |
| experiment | apply some treatment & then to proceed to observe its effects on the subjects. |
| confounding | occurs in an experiment when the effects from two or more variables can't be distinguished from each other |
| random sample | members of the population are selected in such a way that each has an equal chance of being selected |
| simple random sample | of size (n) subjects is selected in such a way that every possible sample of size (n) has the same chance of being chosen. |
| systematic sampling | we select some starting point and then select every ( such as every 50th) element in a population |
| convenience sampling | simply use results that are readily available |
| stratified sampling | subdivide the population into at least 2 diff. subgroups that share the same characteristics ( age or gender) |
| cluster sampling | first divide the population area into sections then randomly select some of those clusters, and then choose all the members from those selected clusters |
| sampling error | is the diff. between a sample result & the true pop result; such an error results from chance sample fluctuations |
| nonsampling error | data is incorrectly collected, recorded, or analyzed |
| fequency table | lists classes or categories of values, along with frequencies, or counts/ of the number of values that fall into each class |
| lower class limits | the smallest numbers that can belong to the diff classes( Rating of 0-3, 3-5// low class lim are 0 & 3. |
| Upper class limits | are the largest # that can belong to the diff classes. ( Ex. 0-2, 3-5 upper class limits are 2 & 5) |
| class boundaries | # used to seperate classes but w/out the gaps created by class limits.( Rating 0-2, 3-5, 6-8, class bound are -.05, 2.5, 5.5 |
| Class midpoints | each class midpoint can be found by adding the lower class limit to the upper class limit and dividing the sum by 2.(Rating 0-2/0+2=2then divide by 2 & you get a midpoint of 1) |
| Class width | the diff. between two conseclower class limits( 0-2, 3-5, 6-8; 5-2=3, 8-5=3; class width of 30 |
| relative frequency table | includes the same class limits as a freq table, but relative are used instead of actual |
| cumulative frequency | for a class is the sum of the freq for that class and all previous classes |
| histogram | bargraph in which the horiz. scale represents classes & the verticale scale represents freq |
| measure of center | value at the center or middle of a data set |
| mean | a set of values is obtained by adding the values & dividing the total by the number of values |
| median | is the middle va;ue when the original data values are arranged in order of increasing or decreasing (0,1,2,-- 1 is the median) |
| mode | the value that occurs most frequently |
| midrange | value midway between the highest & lowest values in the original data set |
| round off rule | carry one more decimal place than is present in the original set of va;ues. |
| skewed | a distribution of data that is not symmetric and extends more to one side than to the other |
| range | difference between the highest value and the lowest value |
| standard deviation | a measure of variation of values about the mean |
| variance | a set of values is a measure of variation equal to the square of the standard deviation( s = .4767 s(sq)=.23minsq |
| Range rule of thumb | to obtain a rough estimate of the stndard deviation s, (s=range divided by 4) |
| empeirical rule | data sets having a distribution that is approx. bell-shaped, the following prop ally; 68% of all values w/in 1stand. dev.;95% fall w/in 2 stand dev.; 99.7% fall w'in 3 stand. dev. |
| Standard score or Z score | the number of standard deviations that a given value x is above or below the mean( X-mean,diveded by stand dev.) |
| Exploratory data analysis | the process of using statistical tools to invest. data sets in order to understand their imp. characteristics |
| 5-number summary | min value, Q1, Q2, Q3, & the max. value |
| measure of center | mean, median, & mode |
| Measures of variation | stand deviation & range |
| Measures of spread & relative location | Min value, max value, & quartiles |
| Unusual values | outliers |
| Distribution | histograms, stem and leaf plots, & boxplots |
