| Hand in Correlation (thinking): p. 112, 4.36 and 4.37 Applet explorations p. 112, 4.34 and 4.35 correlation meaning 4.26 date heights again You
graphed this by
hand. r = .5653. Now answer the questions. A. If women always married men who were exactly two years older than themselves, what would be the correlation between the ages of husband and wife? (Hint: make a data table and the corresponding scatterplot for 4 or 5 couples with different x's, and look at it.) Correlation (computing & thinking) p. 104, 4.11 (SPSS) gas, speed: association but 0 correlation. Find the means and draw the mean lines on your graph (by hand) to help explain the 0 correlation. p. 104, 4.10 (SPSS) bird colonies again. To add a data pair in SPSS just type them in a new row at the bottom. To delete, click on the case number, which highlights the whole row, hit delete.(This problem looks forward to Ch. 5, sort of) p. 110, 4.28 corn plant density. (SPSS) Notice how the data is entered for SPSS--not as displayed here! but with the first column giving Plants per acre and the second giving Yield. Make a scatterplot. Use your calculator to find the mean yields, and write these on your paper. (Or You can find means for the separate groups in SPSS : in Explore, Plants to the Factor list). Graph the means by hand with a pencil on your printed plot, and connect the means dots. You won't get a straight line. Regression (Ch. 5): Start these, on a separate page. WILL be part of HW assigned next (Day 15): C. Use the SPSS Scatterplot handout and graph the regression line for govsal on avgpay (as shown, back page), also the lines for the 4 separate groups (either on one graph or on panels.) Print them out and keep them. Start answering questions 6-11, on p. 3 of the handout. Keep the handout answers till you can answer all 12 questions. p. 118, 5.1 IQ and reading scores. Graph, slope, predict. Notice we don't have a scatterplot of the data, only this straight-line summary. p. 139, 5.24 Penguins diving Again, we don't have a scatterplot, only the summary. p. 122, 5.4 (SPSS) Sparrowhawk colonies Use SPSS to make the scatterplot, with the line, and find r. Do (c), and compute (d) by hand. Now use the "up and over" method of Fig. 5.1, p.116, with a pencil and straightedge to mark the predicted value from (d) on the y-scale. Write down your computed answer next to it. Make sure the two methods give consistent answers. Some more with SPSS--as long as you're at the computer, get r's, the graphs and lines: p. 140, 5.26 (SPSS) sisters & brothers p. 146, 5.42 (SPSS) A computer circle game The last part of the last question, "Give numerical measures that describe the success of the two regressions," is asking for you to use Fact 4. |
Read, to
discuss p. 112, 4.33 Do a rough sketch for yourself. Look at all the graphs you make, and guesstimate the correlation coefficient (before you read or calculate it.) Regression: Use http://www.whfreeman.com/bps4e, Correlation and Regression applet . p. 148, 5.55 |
Optional
Do now if you need the practice: Straight line graphing practice: A. y = -10 + 3x, graph for 2<x<10. B. y = 500 - 20x, graph for 0<x<10. Correlation: Use http://www.whfreeman.com/bps4e, Correlation and Regression applet (see Day 13 for details) to make different scatterplot patterns, and observe their r's. 4.28, I said to
draw the line by hand.
|
Exam
2 a week from Friday: Day 19 (Oct. 5. Day before
break. Let me know Right Away if you need to take the exam
early (Wed. or Th.)).
Starts with Ch. 3, Normal distribution,
tables.
Thru Ch. 4, and what we cover of Ch.5 through next Monday. Sample
exam available Fri. One
sheet of notes: I will give you paper
copies of the Normal table.
Relationships: (BPS4e,
Ch. 4) Day
13
Homework questions?
Who are those outliers in the educ-v-mortality.sav
plot?
Timeplots: are scatterplots, where the x axis shows time.
(often
a lurking variable: plot data against order of taking
observations)
Handout on SPSS Scatterplots etc.
pp.1-3, p.4
, showing subgroups, labeling individual points.
govsal_vs_pay.sav
is the file used for most of the handout. (In SPSS for Class BPS
folder)
Correlation Day 13
r: strength of LINEAR relationship. -1 (perfect negative
relationship) to +1 (perfect positive relationship). No units. Sensitive
to outliers. Look at quadrants made from mean lines to guesstimate it.
Calculating:
Montana (17,895,
55,502) Govsal = 28,569.69 + 2.71*avgpay
Predicted
Govsal
= 28,569.69 + 2.71*17,895 = 28,569.69 + 48,495.45 = 77,065.14
(higher than actual)
a is y-intercept.
b is slope:
If x increases one unit, yhat increases b
units.
(b multiplies the x-variable.)
If you know that yhat increases 12 units for every one that x
increases, you know that the slope of the line b = 12.
Governor's salaries increase (on the average across the states)
$2.71 for every increase of $1 of average pay.
This is a summary of the linear
relationship, in the same way that the mean of a distribution is one
summary of the distribution. Particular states won't match this
exactly.
(In a straight-line relationship, the amount that y
increases
for one unit increase in x is the same no matter what value of
x
you start with) RegressionSlope.xls
or
in ClassMaterial\Math151-BPS4e \RegressionDemos Excel BPS4e
| Sievers home | Math151-Fall07/Dayf14.htm | 1pm | 9/24/07 |