Data Analysis DP1a 1c Frequency charts Bar graphs histograms stem & leaf plots Appropriate Data Displays

BELL Ringer Define : Population Define: Sample

Population: The entire group of people or objects that you want information about Sample: The part of the group that is actually surveyed.

Biased versus unbiased questions Biased  slanted Can be by question or sample Question is biased if the answer goes one particular way. A group is biased if it is “prejudiced”towards one particular answer.

TYPES OF GRAPHS title J F M A M

Test Scores Out Of 100 StemLeaf Stem-leaf chart sort the data from smallest to largest find the range of the data consider, typically, 3 significant (or less) digits each number is broken into a stem value (first 2 digits) and a leaf value (next digit) plot each leaf against each stem sort leaves within each stem The resulting stem-leaf chart is similar to a histogram but all the actual data values can be extracted. This allows the user to find certain percentiles.

Frequency chart count the number of occurrences of each value Interval/Ratio scale frequency chart divide range of data values in a small number of equal sized intervals choose appropriate endpoints for each interval decide where values that fall on endpoints will fall count the number in each interval (tally marks)

Times hands washed TallyFrequency Hand Washing Survey

Histogram for Hand Washing Survey Times hands washed TallyFreq. 0-3||||| |6 4-7|||||5 8-11|||| ||||| ||7 Hand Washing

Choosing appropriate graphs? Circle graph  percentages Line graph  Change over time Histogram  Intervals needed Stem & leaf plot Group data in ordered list Bar graph Distinct categories

Population definition characteristics Examples from your life illustration

Misleading graphs Graphs that are accurate – represent the data but can lead the viewer to different conclusions.

Gap in data Bars not same width Colors – some very bright others pale and fade into graph

Scale too small or too large to get an accurate view of the differences between categories. go up by 1’s when data is 100, 125,175 Intervals equal but data spread does not match – data 1, 2, 12, 13,14,23,24,25,29,30,32 Intervals

You are to create two graphs – both will represent the same data and will be accurate; but one will be misleading.