After the Launch is complete, I let my students know that two way tables are often used to analyze survey results. I say, "When a lot of information is obtained, it is often helpful to condense this information into a table by grouping the data into categories. A two-way table is one way to do this." Then I will demonstrate how the rows indicate one category and the columns, the other category.
Next, I announce to the class that we will be collecting data using a survey method today. Our sample for the survey will be the class. I project Tables A and B on the board. I tell the class that each student should go up to the board in an orderly manner and mark a tally in an appropriate box in each of the two tables.
- Table A is the Facebook/Twitter table
- Table B is the Gender/Body Piercing table (For Table B, I make it clear that it refers to piercing made by personal decision, not done by parents when they were infants.)
Once all students make one mark in each table, they should tally the marks and complete the tables at their desks with a partner. Here is an example: Board and Student Table Example.
As my students work on the task I watch out for a common mistake: adding the bottom row and far right column of "totals" and placing this value in the lower right hand box. Actually this number should be the sum of either the bottom row, or right column. In my case this number is 19. Students may write 38.
When the students have completed their tables, I introduce the term frequency as the statistic that describes the number of tallies in each box. We will discuss the relevance of the frequency to the categories in each table, making connections to our class (since this data describes us).
Зарубежные ученые-математики проверили «Попрыгунчика» и единодушно подтвердили его высокое качество. Они заявляли, что это сильный, чистый алгоритм, который может стать отличным стандартом шифрования. Но за три дня до голосования в конгрессе, который наверняка бы дал «добро» новому стандарту.