ITSACORR is a popular programme for statistical analysis of an interrupted time-series (e.g. to see if there's a change in trend in a series of numbers, such as the daily responses of a subject). As I mentioned in a previous post, given the unavailability of its originator, John Crosbie (Crosbie, 1993), I seem to have accidentally become the (possibly) sole custodian and supplier of the programme.
However, as I also pointed out, Huitema (2004) has strongly criticized the method and recommends that it not be used. I wrote to Huitema recently and asked him whether he had an alternative to ITSACORR to offer. He sent me a nice reply, along with a manuscript which again evaluates ITSACORR, and again concludes that it has "fatal flaws". He does have an alternative programme to offer. It's available at http://www.stat.wmich.edu/slab/Software/Timeseries.html Unfortunately, it's not as user-friendly as the now-discredited ITSACORR, lacking a cookbook example to explain its use and how to do data entry in matrix format. He promises an article "later this year" which should provide help for the statistically-challenged (i.e. me). He offers these references (quoting from his letter): ---------- McKnight, S., McKean, J. W., & Huitema, B. E. (2000). A double bootstrap method to analyze linear models with autoregressive error terms. Psychological Methods, 5, 87-101. Examples of the required design matrices can be found in the appendix of: Huitema, B. E. & McKean, J. W. (2000). A simple and powerful test for autocorrelated errors in OLS intervention models. Psychological Reports, 87, 3-20. Details on why the matrix form has been specified as it has can be found in: Huitema, B. E., & McKean, J. W. (2000). Design specification issues in time-series intervention models. Educational and Psychological Measurement, 60, 38-58. -------- My references: Crosbie, J. (1993). Interrupted time-series analysis with brief single-subject data. Journal of Consulting and Clinical Psychology, 61, 966-974. Huitema, B. (2004). Analysis of interrupted time-series experiments using ITSE: A critique. Understanding statistics, 3, 27-46.[available on-line at http://www.leaonline.com/doi/pdf/10.1207/s15328031us0301_2 Stephen ___________________________________________________ Stephen L. Black, Ph.D. ([EMAIL PROTECTED]) Department of Psychology Bishop's University Lennoxville, QC J1M 1Z7 Canada Dept web page at http://www.ubishops.ca/ccc/div/soc/psy TIPS discussion list for psychology teachers at http://faculty.frostburg.edu/psyc/southerly/tips/index.htm _______________________________________________ --- You are currently subscribed to tips as: archive@jab.org To unsubscribe send a blank email to [EMAIL PROTECTED]
