I agree with the "hold the formula" approach. I introduce Z from the % angle, and I use the "68% - 95% - 99.7%" rules of thumb, and occasionally substitute "most people" "nearly everybody" and "virtually everybody" for the %. You can get a lot of mileage from this approach. The formulas can be introduced later, when dead reckoning fails.
Say, anybody else notice that students are showing up to their first stats class with overly-expensive calculators? I had a student with a graphing TI, she lost the manual, and couldn't get a mean! Being a "HP" person, I couldn't get the mean either! ============================================ John W. Kulig Professor of Psychology Plymouth State College Plymouth NH 03264 ============================================ "Eat bread and salt and speak the truth" Russian saying. -----Original Message----- From: Mike Scoles [mailto:[EMAIL PROTECTED] Sent: Tuesday, February 25, 2003 12:08 PM To: Teaching in the Psychological Sciences Subject: RE: z-score woes Many students have trouble with z-scores because they are introduced with a formula. I have had success by starting with various standard scores (IQ, GRE, T, z). After describing IQ scores, I give a few prompts like, "What is another way of saying that someone has an IQ of 115? 70? Someone 2 standard deviations above the mean would have what IQ score?" Then I do the same for GRE, T, and z. Then I ask them to translate one type of score to another--"An IQ of 115 would be the same as a T of what?" They can easily do all of this without z = (X - mean)/SD or X = mean + z(SD). Those formulas help when you don't have nice round numbers, but a lot of drill without the formulas pays off. It is much easier for students to see how to use the formulas to translate from one scale to another once they have done it without them. ************************************************* Michael T. Scoles, Ph.D. Director, Arkansas Charter School Resource Center Associate Professor of Psychology & Counseling University of Central Arkansas Conway, AR 72035 voice: (501) 450-5418 fax: (501) 450-5424 ************************************************* >-----Original Message----- >From: Robert Grossman [mailto:[EMAIL PROTECTED] >Sent: Tuesday, February 25, 2003 6:39 AM >To: Teaching in the Psychological Sciences >Subject: Re: z-score woes > > >> >> Subject: z-score woes >> "I have a student who just does not understand z-scores. I have >met with him for at least two hours outside of class and he still >doesn't understand the concept. In particular, he doesn't seem to >understand why you need to include standard deviation in the >calculation of z-scores. "Why can't you just compare the raw >> scores?" is his frequent question." > >Rod, > >I would suggest you give him a real problem we face in our >admissions process. Say you have two students and can only admit >one. They should be equal in most respects but have very >different test scores--one has a SAT scores V 500 + M 450 = 950 >while the other has an ACT Composite of 32. Which has a better >chance of doing well in college? This isn't raw score comparison >but the numbers paint one picture while the z-scores give quite a >different picture. > >bob grossman >[EMAIL PROTECTED] >Kalamazoo College > > --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED] --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED]
