4.2 Displays of Quantitative Data

Stem and Leaf Plot A stem-and-leaf plot shows data arranged by place value. You can use a stem-and-leaf plot when you want to display data in an organized way that allows you to see each value.

Stem and Leaf Example StemLeaf

The 5 Number Summary and the Box and Whisker plot (boxplot) The five number summary is the statistics used to create box and whisker plot. The five number summary consists of :  We compute these with the 1-var Stats SymbolNameDescription MinXMinimumLowest data value in this sample Q1Quartile 125% of our data is below this and 75% of our data is above this MedMedian50% of our data is below this and 50% of our data is above this Q3Quartile 375% of our data is below this and 25% of our data is above this MaxXMaximumHighest data value in this sample

DOT PLOTS A data display in which each data item is shown as a dot above a number line In a dot plot a cluster shows where a group of data points fall. A gap is an interval where there are no data items. Is this data skewed left, symmetric or skewed right? How can you tell?

Graphing The Data Notice, the Box includes the lower quartile, median, and upper quartile. The Whiskers extend from the Box to the max and min. Minimum Quartile 1 Median Quartile 3 Maximum

Frequency Table A frequency table shows the number of pieces of data that fall within given intervals.

Frequency Tables Price $TallyFrequency Scale- includes the least value and greatest value Interval- Separates the scale into equal parts

Histogram A histogram looks very similar to a bar graph. There are three important differences between a histogram and a bar graph. 1. On a Histogram, the bars will touch. 2. On a Histogram, we label the dividing lines between bars, not the bars themselves 3. Histograms are used for QUANTITATIVE data, while bar graphs are used for QUALITATIVE data.

Lung Volume Data Lung volume (litres)Frequency 2.5– – – – – – –5.91

Histogram of Lung Volume Data Lung Volume Number of Patients