The Worst Mistake Made on a Dissertation Is...

I have a saying that I like to tell consulting clients, which is easier said than done, but I think are words for doctoral candidates to live by: "The only bad dissertation draft is one that isn't turned-in." The most common factor that unnecessarily slows progress on a dissertation proposal or defense is a propensity to strive for the perfect draft. As a graduate student, we all fantasized of turning-in our first draft and having our advisor, being so amazed at its brilliance, insist that you accept your PhD on the spot.

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Coming Soon: Stats Make Me Cry Bookshelf

Searching for a good resource on a complex stats topic can be exhausting, not to mention overwhelming. The Stats Make Me Cry Bookshelf will be a dynamic list of the most helpful books on various statistical topics. Users will be able to submit books for inclusion in the list, comment on existing books in the list, and vote books up or down the list. In addition, links to sites where they can be purchased will be provided for all books on the list. For the record, I have no vested interest in any stats books, so all books will be posted solely on merit. Please feel free to submit books to be considered for inclusion, using the form in the left sidebar! Thanks!

I Am Now Hosting Periodic Google+ Stats Make Me Cry "Hangouts"

A Google+ "Hangout" allows up to ten people to video chat simultaneously, with one person having the ability to moderate. I am now hosting a stats "hang-out" periodically (had two thus far), during which users attend on a "first come" basis and discuss stats issues and questions!

Here is how it works:

Readers interested in participating simply need to add their name and Google email address (@gmail) to my hangout list (or circle, as Google calls it), by using the form in this page's right sidebar. If you are already a "Google +" user, I'll add you to my "Stats Hangout" circle and from that point forward you will have access to the "Stats Hangouts", as they begin.

If you are not a "Google+" user, I will be happy to send you an "invite" to join (which is fast, easy, and free).

Watch the brief video below to see how Google+ hangouts work!

I'm looking forward to trying this idea and chatting with all of you with stats questions (or who just want to discuss stats)!

Moderating Effects with Seemingly Uncorrelated Variables

I received a great question this week, as a submission to my Ask the Stats Make Me Cry Guy page, which asked: In order for a moderating relationship to exist, do the predictor IV and dependent variable need to be significantly correlated?". This is a question that I am asked a lot, partly because of the common confusion between mediators and moderators and the commonly held belief that an IV and DV should be related for mediation to be present (see my video blog on Mediators, Moderators, and Supressors for more info on this topic). However, moderators are a completely different story. In fact, a simple correlation between two variables can be very misleading, if one relies on it as an indicator of potential moderating effects and/or as an indicator that moderating effects should be tested.

Imagine the circumstance where you are testing whether there is an association between "number of carrots consumed" and "blood pressure". Imagine further that you have reason to believe that the association between these two variables varies by age (for this example let's make age dichotomous, i.e. old vs. young). Perhaps you expect that the more carrots someone eats, the lower their blood pressure will be (negative association), but you think this will be more true for older people than younger (i.e. age moderates the effect of carrot consumption on blood pressure).

Since you'd expect that the association will probably still be negative in both groups, but more negative in older people (if your hypothesis is accurate), you might expect to see a graph like the one below:

This graph is fairly typical of a two-way interaction, where the two groups (young vs. old) have differing slopes. Since both group's slopes are negative, it isn't supriising that the overall sample slope is also negative. However, imagine a slightly different scenario where younger people's slope was actually positive for some unknown reason. In this case, your graph would look like this: In this scenario, you would still likely have significant moderation (probably an even strong interaction effect, since the difference in slope is even larger), however you might not see a significant association between the IV (carrots) and DV (Blood Pressure) in the sample as a whole. This example highlights the danger of relying only on correlations and failing to consider/test potential moderating effects. Thanks for the great question, Ken!

Using Syntax to Assign 'Variable Labels' and 'Value Labels' in SPSS

Preparing a dataset for analysis is an arduous process. Besides recoding and cleaning variables, a diligent data analyst also must assign variable labels and value labels, unless they choose to wait until after your output is exported to Microsoft Word. Unfortunately, that option only leaves additional opportunity for error and confusion, not to mention the inefficiency of editing tables in Microsoft Word. Who among us have not been frustrated while wrestling with Microsoft Word?

When used in conjunction with the customizable SPSS table "Looks" function, formatting your variable labels and value labels can make your SPSS results tables nearly ready for publication, immediately after analysis (CLICK HERE FOR TUTORIAL VIDEO ON TABLE "LOOKS")! Fortunately, SPSS syntax offers a fairly straightforward method for assigning proper labels to both your variable labels and value labels.

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How to make SPSS produce all tables in APA format automatically!

Updated on Wednesday, June 8, 2011 at 3:43PM by Jeremy Taylor

Formatting a graph that was exported from SPSS to Microsoft Word can be an absolute pain. Since neither program is known for it's simplicity or "user-friendliness", the interaction between the two can be predictably tedious and frustrating. The process of converting a standard SPSS table to APA format might be bearable, when you are talking about a single table, but can become overwhelming when you have an entire manuscript worth of tables. Fortunately, a few minor alterations to your SPSS settings can make SPSS do most of the heavily lifting for you, making SPSS automatically produce tables that closely resemble APA format and cutting down your formatting time by as much as 90%!

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Stats Make Me Cry was recognized today as one of the top 40 stats blogs! Check it out: http://bit.ly/dXgIj4

In their blog "40 Fascinating Blogs for the Ultimate Stats Geek", bschool.com ranked Stats Make Me Cry in the top 25! I'm very excited and will strive to move up the list!

http://bit.ly/dXgIj4

Check Out This Great Post About Confusing Stats Terms at the "Analysis Factor"!

No new blog this week, because I'm out voting! However, i did come across a great blog about other confusing stats terms at the "Analysis Factor"! Check it out: http://bit.ly/btqo2u

Top Ten Confusing Stats Terms Explained in “Plain English” (#8: Residual)

When I hear the word "residual", the pulp left over after I drink my orange juice pops into my brain, or perhaps the film left on the car after a heavy rain. However, when my regression model spits out an estimate of my model's residual, I'm fairly confident it isn't referring to OJ or automobile gunk...right?  Not so fast, that imagery is more similar to it's statistical meaning than you might initially think.

In statistics, a residual refers to the amount of variability in a dependent variable (DV) that is "left over" after accounting for the variability explained by the predictors in your analysis (often a regression). Right about now you are probably thinking: "this guy likes the word "variability" way too much, he should buy a thesaurus already!"

Let me try again: when you include predictors (independent variables) in a regression, you are making a guess (or prediction) that they are associated with the DV; a residual is a numeric value for how much you were wrong with that prediction. The lower the residual, the more accurate the the predictions in your regression are, indicating your IVs are related to (predictive of) the DV. Keep in mind that each person in your sample will have their own residual score. This is because a regression model provided a "predicted value" for every individual, which is estimated from the values of the IVs of the regression. Each person's residual score is the difference between their predicted score (determined by the values of the IV's) and the actual observed score of your DV by that individual. That "left-over" value is a residual.

L ike the imagery of the orange pulp, a statistical residual is simply what's left over from your regression model. They can be used for many things, such as estimating accuracy of your model and checking assumptions, but that is a chat for another time...

Top Ten Confusing Stats Terms Explained in “Plain English” (#9: Multicollinearity)

Multicollinearity said in "plain English" is redundancy. Unfortunately, it isn't quite that simple, but it's a good place to start. Put simply, multicollinearity is when two or more predictors in a regression are highly related to one another, such that they do not provide unique and/or independent information to the regression.

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Live "Facetime" Chat Stats Consultation Now Available!

For those of you that have an iPhone 4, I am now able to offer live Facetime chat stats consultation to registered clients! Please let me know if you are a current client and would like to use this feature at no additional cost!

Top Ten Confusing Stats Terms Explained in “Plain English” (#10: Standard Deviation)

Most people find statistics to be complicated, confusing, and just generally frustrating. One of the biggest causes of confusion is the complicated vocabulary that is associated with stats. Frankly, it sometimes seems that stats terms were made to be intentionally complicated. In fact, some concepts seem perfectly understandable when described inplain English, but seem incomprehensible when described in stats lingo.

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Top Ten Tips for Data Analysis to Make Your Research Life Easier!

While there is no "magic bullet" to make stats and data analysis easy to understand and helpful in our research, there are some things that you can do to avoid pitfalls and help things run smoothly. This "top ten" list offers a few of those things that I think you will find helpful! I'll be posting a video of this list later today on my Stats Videos page.

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What Makes Stats Scary or Confusing? I Want To Hear From You!

I want to write about and make video tutorials about the things that you want to hear about. Please respond to this post with a comment about what you think is scary or confusing about statistics!

New Video Stats Tutorial Page at Stats Make Me Cry!

Stats Make Me Cry has undergone a bit of a restructuring. Due to fantastic popularity, our Deviant Square Video Stats Tutorials have been given their own webpage! This will allow our episodes to be easier to find and easier to be browsed through. The link for our videos page can be found in the menu bar and in our sidebar (as well as below). Thanks and keep watching!

FIND THE VIDEO STATS TUTORIAL PAGE HERE!

Average American Project LIVE Analysis Tuesday Morning at 9AM CST!

Less than 24 hours until the Average American Project live data analysis that has been collected over the last few weeks. Thank-you again to everyone that has been a part of the analysis. The collection has been a great success and I look forward to the analysis to take place live in the morning! Once again, the analysis is set to take place at 9AM on Tuesday (July 13th, 2010). A link will appear below this blog entry about 15 minutes before the start of the broadcast that will allow viewers access. There will also be a live chat available for you to ask questions about the analysis!

The LIVE data analysis is complete and was a great success! It will be posted as Episode 6 of my Deviant Square Video Podcast Tutorial series !

Within-Subject and Between-Subject Effects: Wanting Ice Cream Today, Tomorrow, and The Next Day…

The conceptual difference between within-subject and between-subject effects is something I am asked about quite often. So often in fact, I thought a blog posting was warranted! As a quick disclaimer, I know this is a complex issue and the description of what each type of effect actual is varies greatly based on the kind of analysis one is conducting. However, what follows is an attempt to provide a basic conceptual foundation to understand the differences.

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Bonferroni Correction In Regression: Fun To Say, Important To Do...

The Bonferroni correction is only one way to guard against the bias of repeated testing effects, but it is probably the most common method and it is definitely the most fun to say. I've come to consider it as critical to the accuracy of my analyses as selecting the correct type of analysis or entering the data accurately. Unfortunately adjustments for repeated testing of hypotheses, as a whole, remains something that is often overlooked by researchers and the consequences may very well be inaccurate results and misleading inferences. In this independence day blog, I'll discuss why the Bonferroni Correction should be as important as apple pie on the 4th of July.

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Stats Make Me Cry is excited to announce a new affiliation with "The Analysis Factor"

Stats Make Me Cry is proud to announce our new affiliation with The Analysis Factor. The Analysis Factor, is another wonderful resource for stats information, Webinars, newsletters, and much more. Owner and Operator Karen Grace-Martin, author of the book Data Analysis with SPSS, 3rd Ed., is a very knowledgable and experienced statistician, as well as an excellent teacher! We are excited and proud to be affiliated. Check out their website and sign-up for a stats Webinar today!

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Go Blackhawks! Day After Pics

I know this is not stats-related, but I am still a Chicagoan, so I must show the pride! I also got some camera footage of the scene on Clark and Addison, as well as Rush and Division that I'll try to post later. Go Hawks!

Update: i posted the video footage of the celebration on our "fun stuff" page, check it out!

http://www.statsmakemecry.com/fun-stuff/