Displaying Quantitative Data with Histograms 1.2 cont. Hw: pg 45: 53, 56, 57, 59, 60, Target Goal: I can construct a histogram by hand and with the calculator.

Displaying Quantitative Variables Histograms The most common graph for distribution of one quantitative variable. No spaces between groups.

How to construct a histogram 1. Divide range of data into classes of equal width and count number of observations in each class; be sure to specify classes precisely so that each observation falls into exactly one class. 2. Label and scale axis and title graph! 3. Draw a bar that represents the count in each class.

Remember: Leave no space between bars. Leave no space between bars. Add a break-in-scale symbol (//) on an axis that does not start at 0. Add a break-in-scale symbol (//) on an axis that does not start at 0. 5 classes is a good minimum. 5 classes is a good minimum. Histogram Tips (page 39) Histogram Tips (page 39)

Example Drive Time Professor Moore, who lives a few miles outside a college town, records the time he takes to drive to the college each morning. You previously entered the times (in minutes) into a list name “DRVTM” (pg.46, ex. 55) for the 42 consecutive weekdays, with the dates in order along the rows.

. a. Fill in freq. column and construct histogram. Drivetime Frequency

B. Graph (Note: Your graph needs to be specific) B. Graph (Note: Your graph needs to be specific) Is the distribution roughly symmetric, clearly skewed, or neither? Are there any clear outliers? The distribution is roughly symmetric with no clear outliers.

c. Make a calculator histogram of these drive times. Make calculator histogram and use the trace key. STATPLOT:Plot1:On STATPLOT:Plot1:On –Xlist:2ndSTAT:DRVTM:ENTER –Freq:1 (sometimes need to press ALPHA 1) Window Window –Xmin=6, Xmax=11, Xscl=.5, ymin=0, ymax=13, yscl=1,xres=1 Use the following classes and determine frequencies. Use the following classes and determine frequencies. Can use Technology Toolbox as reference(p.38) Can use Technology Toolbox as reference(p.38) Used throughout the book to guide you step by step through various calculator functionalities. Used throughout the book to guide you step by step through various calculator functionalities.

Using Histograms Wisely 1. Don’t confuse histograms with bar graphs. Bar Graph: ____________, compares the distribution of ______________. Histograms: ______________, the distribution of ______________________.

2. Don’t use counts (freq) or percents (relative freq) as data. Length: Count: Graphed IncorrectlyDraw Graph Correctly

3. Use percents instead of counts on the vertical axis when comparing distributions with different numbers of observations. Mary compared the number of letters in the first 200 words of a medical journal and of the first 100 words of an article from an airline magazine.