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S.O.C.S?
- Shape: symmetric (normal curve); Skewed Right or Skewed Left
- Outliers: 1.5(IQR). IQR? Q3-Q1
- Center: Value that divides the distribution so that half are larger and half are smaller
- Spread: Smallest and largest value
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When to use dotplots?
categorical variables.
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When to use barcharts?
compare the sizes of categories or groups. Sizes can be measures as frequencies or percentages.
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When to use Histograms?
large data sets involving quantitative variables.
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When to use Stemplots? what's the difference beween histograms and stemplots?
histograms: show many scores that fall into each group but the exact values are often lost.
Stemplots show these exact values.
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What to use for categorical data?
dotplots and bar charts.
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What to use for quantitative?
histograms, cumulative frequency plots (ogives) and stemplots.
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Steps when looking for a variance:
*see page 60 Barron's*
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What's the empirical rule?
68-95-99.7
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What happens to the spread after adding the same constant to the mean and median?
stays the same
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relationship of the mean and median on...
-skewed left
-skewed right
- -mean is less than the median
- -mean is usually greater than the median
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make a least square regression line on the calculator. *page 113*
*pg. 113*
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what's correlation? *definition*
correlation r is equal to the slope of the regression line when z-scores for the y-variable are plotted against z-scores for the x-variable.
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which are affected by the outliers?
Mean, Standard Deviation, Range
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what will cause a greater power of a test?
- -larger sample size
- -larger alpha
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when do you use a significant test?
- when testing a claim.
- ex: ho; ha
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what's true about the t-distribution?
- -there are different t-distributions for different values of df( degrees of freedom)
- -bell-shaped and symmetric
- -more spread out than the normal distribution
- -the larger the df value, the closer the distribution is to the normal distribution
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what's systematic sampling?
- -list the population in some order
- -choose a random point to start
- - i.e. picking every 10th, 50th, etc.
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What's stratisfied sampling?
- -population is divided into homogenous groups called stratas. random samples from each strata are chosen.
- -stratify by age, gender, income level etc.
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cluser sampling?
- population is divided into heterogenous groups called clusters.
- -take a random sample of clusters.
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2-sample confidence interval Mean
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2-sample confidence interval Proportions
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2-sample significance test Mean
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2 sample significant test proportion
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1-sample significant test mean
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1 sample significant test proportion
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1 sample confidence interval
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1 sample confidence interval proportion
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you've made a confidence interval and you want to see if there's a difference between the two means. the interval is -1.3692, -.0308. is there a difference?
since it does not reach 0, there is evidence that there is a difference between the two means.
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