Wednesday, October 14, 2009
Wednesday, October 07, 2009
Review answers
b) 233.5: For each year that goes by we predict about 233.5 more aircraft flying.
c) 89.9% of the variation in aircraft flying is explained by regression on year.
d) Plug in 2 (not 1992!): predicted aircraft = 2939.9+233.5*2 = 3406.9 aircraft.
e) residual at 2 = 40, so the actual was 3406.9+40=3446.9 or 3447
f) sqrt(.899) = .948 = strong, positive, linear relationship between year and aircraft.
g) On average, my predicted number of aircraft misses by about 33.43
h) aircraft-hat = 2939.93 + 233.5(year)
i) we predict in 1990 that the number of aircraft flying is about 2939.9
Study hard! I hope this helps!!!
Tuesday, October 06, 2009
Thursday, September 24, 2009
Regression practice
#28 all + (e) interpret slope
#33 all + (f) interpret r + (g) interpret r^2
Monday, September 21, 2009
Thursday, September 17, 2009
Tuesday, September 15, 2009
some review ideas, Unit 1
Q1 - 1.5IQR
Q3 + 1.5IQR
sd is always positive
(or zero if all the data is identical)
Categorical graphs:
bar and pie
Quantitative graphs:
stem and leaf (shows data)
boxplot (can hide shape)
ogive/cumulative freq
dotplot
histogram
Independent data makes bar graphs with similar levels
The mean is lower than the median for skewed left data
Measures of spread: IQR, sd and range
Measures of center: mean and median
Which of the above are resistant? med and IQR
Rule of thumb: 68-95-99.7
z-score formula: (x - mu)/sigma
Monday, September 14, 2009
Wednesday, September 09, 2009
normal cdf
Answers:
a) Only 0.07% of tires last longer than 40,000 miles. Not very likely!
b) 21.19% (z score is -0.8)
c) 67.31% (z scores are -0.8 and 1.2)
Tuesday night's HW
Page 113 #36
If you ever come looking for homework and I forgot post it, feel free to email me! I check email on my phone too much, so you'll get a fast reply!
Tuesday, September 01, 2009
Monday, August 31, 2009
Review and test
Monday: Unit 1 review, page 105 #7, 16, 21, 29 a-e, 31 and 32
Tuesday: practice, practice. Tutoring
Wednesday: Jeopardy?!?
Thursday: Test (no tutoring)
Friday: StatCrunch in the library computer lab
3-day weekend!!!
Thursday, August 27, 2009
Wednesday, August 26, 2009
Tuesday, August 25, 2009
Sunday, August 23, 2009
StatCrunch this week
- Go to My Groups
- Click on RCHS group
- Click on the First Day of school data
- Make a graph of one or more variables on the survey
- Describe
- Print graph and description
- Find some data. Lots of it.
- You have to find data that contains both categorical and quantitative variables on the individuals.
- Go to My Data
- On the left, you'll see some options, choose the one that works.
- Make sure to Share with our group:
- If you are viewing the data in the StatCrunch, click Edit and then you can share.
- There is a cool new option that will grab data from a website
- Go to http://www.statcrunch.com/
bookmarklet - Go to that page and read about adding a bookmark called "StatcrunchThis".
- Then go to the website you want to grab.
- Click the bookmark
- Save and data and share it.
Thursday, August 20, 2009
Wednesday, August 19, 2009
data, data
Ch. 4 #9, 12, 17, 24
Don't forget: if technology fails you, just make a dotplot!
Or you could try making a graph on Statcrunch!
#24 is a problem with statistics done WRONG. You task is to figure out what is wrong.
Tuesday, August 18, 2009
Monday, August 17, 2009
Thursday, August 13, 2009
independent?
In class we did Ch. 3 #17 and 18
For homework: Ch. 3 #15
Monday, August 10, 2009
Saturday, August 08, 2009
Stat Crunch instructions
Thursday, May 07, 2009
Competition Information
Friday, May 01, 2009
resources
Last weekend!
Thursday, April 30, 2009
Friday review session
Wednesday, April 29, 2009
Tuesday, April 28, 2009
Monday, April 27, 2009
Web site for Name that Test!
However, I think that after you 10 or so of these, you'll get used to the wording of this site and it will be good practice.
Note: this website includes prediction intervals, which you do not need to know.
Monday, April 20, 2009
Friday, April 17, 2009
Thursday, April 16, 2009
Wednesday, April 15, 2009
Tuesday, April 14, 2009
Friday, April 10, 2009
probability
Thursday, April 09, 2009
Wednesday, April 08, 2009
Review so far
Friday, April 03, 2009
Thursday, April 02, 2009
a little of this, a little of that...
Tuesday, March 31, 2009
Tuesday, March 17, 2009
CLT video
This should help you think about the Central Limit Theorem
Monday, March 16, 2009
Thursday, March 12, 2009
practice, practice
The X^2 for the evens are: 3.677, 290.131, 479.508 (listed in no particular order!). But that lets you check your work, at least a little bit!
Wednesday, March 11, 2009
Tuesday, March 10, 2009
Tuesday, March 03, 2009
Thursday, February 26, 2009
Wednesday, February 25, 2009
Monday, February 23, 2009
Thursday, February 19, 2009
Tuesday, February 17, 2009
Chapter 21 recap
The bigger the sample size, the more power we have.
We also lower our chances of making either error.
More Sample Size!
We need to be careful with REALLY big sample sizes.
The standard deviation gets really small and you'll always get a small p-value.
This can cloud practical significance: use a confidence interval instead!
Ho is false!
If the Ho is really false, we have lots of power and very little Type
II error (dumb criminal).
If the true value differs only slightly from the Ho, we have little
power and may make a Type II error. (smart criminal)
This is called effect size.
Changing alpha
Making alpha smaller (0.01) makes it harder to reject.
We do this if want less Type I, but are willing to tolerate more Type
II and less power.
i.e., death penalty
Alpha and medicine
If the established treatment is highly effective, you demand a very
small p-value before rejecting (low alpha).
If the standard treatment is not very effective and you have reason to
believe it can be easily improved, you would be more willing to accept
a new treatment even though the p-value is larger (higher alpha).
Thursday, February 12, 2009
Monday, February 09, 2009
Monday, February 02, 2009
Monday, January 26, 2009
Wednesday, January 21, 2009
Monday, January 12, 2009
Wednesday, January 07, 2009
Tuesday, January 06, 2009
Monday, January 05, 2009
Wednesday, December 17, 2008
Tuesday, December 16, 2008
Wednesday, December 10, 2008
Monday, December 08, 2008
Tuesday, December 02, 2008
Wednesday, November 12, 2008
Wednesday, November 05, 2008
Tuesday, November 04, 2008
Monday, November 03, 2008
Tuesday, October 28, 2008
just a bit
Finish #4: graph and algebra
On the ball lab: are the graphs continuous or discrete? what are the
y-intercepts?
Monday, October 27, 2008
Monday, October 20, 2008
Thursday, October 16, 2008
Monday, October 13, 2008
Tuesday, October 07, 2008
end of chapter 8
Notes from today in class:
- What the heck is a "line of best fit"?
- Its real name is: Least Squares Regression Line!
- Or: LSRL
- Least squares? least squares of what?
- The sum of all the residuals squared is as small as possible!
- Regression? What does that word mean?
- r tells us how much to regress to the mean (example…)
- And speaking of mean:
- (x-bar, y-bar) is on the line (duh!).
- And btw: the residuals always add up to zero.
- You should also note that if you switch x and y, the correlation does not change, but the LSRL does.
- You should never use a LSRL to predict x using y. It is not created to minimize the predictions for x, only for y.