Mr. Ohashi's Math Homepage

DAILY MATH CLASS SUMMARY
What did we do in class today?

1st Quarter ~ 2nd Quarter ~ 3RD QUARTER ~ 4th Quarter

Wednesday, 2/8

Purpose Statement: Examine graphs in order to see how they can be misleading.
Handouts: Misleading Graphs (Turn in: Thurs, 2/9)

We know that we can use data to support arguments, but we can also use graphs to do that. Suppose we surveyed students to see whether they liked math or science better and put the results in a bar graph. We could make our bar graph imply anything we'd like...

The first bar graph shows the data with a standard scale. We can clearly see that 16 students selected math and 12 students selected science.

If you change the vertical scale (like in the second graph), we can make our graph seem like kids like math and science equally even though the data is still the same!

If you change the vertical scale again, this time adding a scale break at the start, we can make our graph seem like WAY more kids like math more than science! Notice that we can use the exact same data to support different arguments.

For classwork, finish #1-5. There is no additional homework tonight, so use that time to get your survey results!

Tuesday, 2/7

Purpose Statement: Use different sized samples in order to compare their reliability.
Handouts: Choosing a Sample Size (Turn in: Wed, 2/8)

Yesterday, we randomly selected 30 students from the 8th grade database on page 33 of your book and used our results to find typical responses. But why did we decide 30? Could we have done less and still had accurate results? That's what we explored today.

We used graphing calculators to randomly select three samples from the database. One sample only had 5 randomly selected students, one sample had 15, and the other had 30. We found the mean of each sample and collected all of the class's data together on line plots. Here's what they looked like:

The actual mean of the 100 students is about 4.22. As you can see, the sample size of 5 has a wide variety of means, and the sample size of 30 has a much tighter cluster of means! The sample size of 30 has data that is much more accurate... almost all of the data are right on the actual mean!

For classwork, finish #1-5. Your homework is to do #8-10.

Monday, 2/6

Purpose Statement: Use random sampling in order to make predictions about a population.
Handouts: Problem 2.3 (Turn in: Tues, 2/7)

Today we did some random sampling! The assignment was Problem 2.3 A-C1 on page 32. You had to randomly select 30 students from the data base on the next page. You then recorded their data and answered some questions.

We used two different random sampling plans to collect the data. For half the data, we used a spinner - we spun twice and that was the student number we included in our survey. For the second method, we used our table of random numbers from our notes - we picked a spot in the table, then took the numbers in pairs and used those as our students to include. Notice that both methods give every student an equally likely chance to be included in our survey!

Your classwork is to finish Problem 2.3A-C1 on p.32. Your homework is a worksheet called Problem 2.3 Homework. Also, I passed out the form that you can collect your survey results on - it is due on Friday, so you have a week to survey people (at least 30)!

Friday, 2/3

Purpose Statement: Quiz today!
Handouts: Brain Teaser (any 8 or back) (Turn in: Mon, 2/6)

We took the quiz today! Your only homework is a Brain Teaser. Have a great weekend!

Thursday, 2/2

Purpose Statement: Review data work in order to get ready for the quiz.
Handouts: Data Quiz Review WS (Turn in: Fri, 2/3)

Today was a review day for tomorrow's quiz. For the quiz, you should be able to:

Make and read histograms

Make and read stem-and-leaf plots

Make and read box-and-whisker plots

Make and read scatter plots

Compare two sets of data and justify statements

We also talked about the survey question that is due tomorrow. Make sure your question is not too personal and is a question that kids will know how to answer!

Your homework is to finish the quiz review. Remember to bring a calculator tomorrow!

Wednesday, 2/1

Purpose Statement: Use what we have learned to analyze survey results.
Handouts: Looking at Survey Data WS (Turn in: Thurs, 2/2)

It was an early release day, so we had a short assignment. For periods 1, 2, and 5, you only need to do #1-4. For periods 4 and 6, you need to finish the entire assignment.

We also started talking about the end of unit project. We are going to conduct a survey. You're job is to come up with a survey question by Friday. Here is the Survey Question handout.

Tuesday, 1/31

Purpose Statement: Consider various ways of sampling in order to make predictions about a population.
Handouts: Selecting a Sample WS (Turn in: Wed, 2/1)

Today we talked about selecting a sample of people in order to conduct a survey. We conduct surveys to find out about a large group of people, but only survey a small group of them because it would be very difficult to ask everyone! Here are the notes we took on the different ways to select who you would include in your sample:

Notice that there are advantages and disadvantages to each sampling method. Some are easier to conduct than others, but the accuracy of their data is not as good. You have to consider both of these factors when deciding on how to select your sample! Remember, the most accurate data will be a random selection that gives everyone a chance to be included in the survey.

The classwork was to finish #1-2. Your homework is #6-7. Don't forget about the quiz on Friday!

Monday, 1/30

Purpose Statement: Use scatter plots to explore the relationship between two variables.
Handouts: More with Scatter Plots WS (Turn in: Tues, 1/31)

We had another day to work with scatter plots today!

The classwork was to finish #1-3. Your homework is #6-7. Also, we have a quiz on Friday!

Friday, 1/27

Purpose Statement: Use scatter plots to explore the relationship between two variables.
Handouts: Scatter Plots WS (Turn in: Mon, 1/30)

Up until now, we have been analyzing one single set of data at a time. Today, we worked with scatter plots, which analyze two sets of data and shows if there is a relationship between the two data sets.

To show the pattern, we draw in a trend line. The line should go through the middle of the data, where about half of the points are above the line and half the points are below. We can use the line to represent the data.

Once you had the line, you had to write an equation for the line. Just like we learned earlier this year, you need to find the y-intercept and the slope to write an equation for a line! When finding the slope, remember to places on the line that are far apart from each other (the accuracy of your slope will be better when the points are far away).

For Monday, finish #1-3. Have a great weekend!