# AP Stats: Chapter 2

 percentile implication if someone scored at the 93rd percentile, that means that in the distribution, 93% of the people earned that score or less how to calculate percentile from data (number of scores below the score) / (total number of scores) cumulative relative frequency graph used to examine a location within a distribution. Groups the observations into equal-width classes, shows accumulating percent of observations as you move through the classes in increasing order how to calculate relative frequency (frequency)/(total frequencies) x100 how to calculate cumulative frequency (frequency) + (frequencies below this frequency) how to calculate cumulative relative frequency (cumulative frequency)/(total frequencies) cumulative relative frequency graph aka ogive interpretation of cumulative relative frequency percentage represents the amount of people at that class or lower ogive aka cumulative relative frequency graph how to calculate z-scores effect of adding or subtracting a constant adds a to the center and location (mean, median, quartiles, percentiles)does not affect shape or measures of spread (range, IQR, standard deviation) effect of multiplying or dividing by a constant multiplies/divides measures of center and location by b (mean, median, quartiles, percentiles)multiplies/divides measures of spread by |b| (range, IQR, standard deviation)multiplies/divides the variance by b2does not change shape density curve a curve that is always on or above the horizontal axis and has exactly 1 area underneath itdescribes the overall pattern of a distribution median of a density curve point with half the area under the curve to its left and  the remaining half of the area to its right, divides the area of the density curve in half mean of a density curve the point at which the curve would balance if made of solid material normal distribution described by the normal density curve, specified by the mean and standard deviation N (μ, σ)mean is at the center of the symmetric normal curve, standard deviation is the distance from the center to the change-of-curvature points on each side inflection point point where the curve changes shape; where the curve changes from a right-side up U to an upside down U common examples of normal distributions scores on tests taken by many peoplerepeated careful measurement of same quantitycharacteristics of biological populations 68-95-99.7 Rule Chebyshev's inequality in any distribution, the proportion of observations falling within k standard deviations of the mean is at least standard normal distribution normal distribution with a mean 0 and standard deviation 1 standard normal distribution standard normal table table of areas under the standard normal curve; table entry for each value z is the area to the left of z; shown in Table A normal probability plot normal probability plot used to assess whether a data set follows a normal distribution how to use a normal probability plot to tell if something is a normal distribution normal if points lie close to a straight lineclear departures from normality indicate that the data is not normal normal cdf calculator function used to find the area of a normal distribution when you have the cutoff points invnorm calculator function used to find the associated cutoff points when you have the area AuthorGymnastxoxo17 ID240910 Card SetAP Stats: Chapter 2 Descriptions Updated2013-10-16T02:26:47Z Show Answers