Statistics (Use Barron's Book)
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- 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
When to use dotplots?
When to use barcharts?
compare the sizes of categories or groups. Sizes can be measures as frequencies or percentages.
When to use Histograms?
large data sets involving quantitative variables.
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.
What to use for categorical data?
dotplots and bar charts.
What to use for quantitative?
histograms, cumulative frequency plots (ogives) and stemplots.
Steps when looking for a variance:
*see page 60 Barron's*
What's the empirical rule?
What happens to the spread after adding the same constant to the mean and median?
stays the same
relationship of the mean and median on...
- -mean is less than the median
- -mean is usually greater than the median
make a least square regression line on the calculator. *page 113*
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.
which are affected by the outliers?
Mean, Standard Deviation, Range
what will cause a greater power of a test?
- -larger sample size
- -larger alpha
when do you use a significant test?
- when testing a claim.
- ex: ho; ha
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
what's systematic sampling?
- -list the population in some order
- -choose a random point to start
- - i.e. picking every 10th, 50th, etc.
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.
- population is divided into heterogenous groups called clusters.
- -take a random sample of clusters.
2-sample confidence interval Mean
2-sample confidence interval Proportions
2-sample significance test Mean
2 sample significant test proportion
1-sample significant test mean
1 sample significant test proportion
1 sample confidence interval
1 sample confidence interval proportion
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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