DISPLAYING QUANTITATIVE DATA CHAPTER 4 We will review last night’s homework and tonight’s homework during next class. We will start class immediately with notes.

I. TYPES OF DISPLAYS A.Dot plots – plots a ‘dot’ for each case against a singe axis. A.Make each dot the same size B.Create a key if the dot stands for more than one unit. C.Ex. How many siblings do you have?

B. STEM AND LEAF PLOTS 1.Gives a picture of the distribution while including the actual numerical values in the graph. 2.Stem is all of the number except the final digit. Leaf is final digit. 3.Write stems in vertical column w/ smallest at the top (Do Not Skip any Stems!!) 4.May want to split the stems to see the distribution better. 5.Write each leaf in the row to R of stem in increasing order from L to R. 6.Provide a key that explains in context what the stems and leaves represent.

B. STEM AND LEAF PLOTS 7.Example. How many pairs of shoes do you own? Number of Shoes owned by Stat females.

EXAMPLE Number of Shoes owned by Stat males. Back-to-back stemplot is good for comparing two groups of the same Variable.

C. HISTOGRAMS 1.Distribution of one quantitative variable that divides the range of data into classes of equal width. 2.Each bin or class includes the 1 st number and goes up to but does not include the last. 3.Y-axis can be the frequency or relative frequency 4.No spaces between groups.

II. DESCRIBING DISTRIBUTIONS A.Shape 1.Modes – how many peaks or bumps there are i.Uniform – no peaks ii.Unimodal – one peak iii.Bimodal – two peaks iv.Multimodal- more than two peaks. 2.Symmetry i.Symmetric – equal on both sides of the center ii.Skewed R – tail on R side iii.Skewed L – tail on L side

II. DESCRIBING DISTRIBUTIONS B.Center – the place on the graph that would divide the area of the two halves equally. i.Mean – used when shape is symmetric or uniform ii.Median – used when shape is skewed. C.Spread – how far away the data is from the center (variability). Calculate the Range. D.Outliers and Gaps – observation that differ from the pattern.