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From |
"Carlo Lazzaro" <carlo.lazzaro@tiscalinet.it> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: R: which statistics to use |

Date |
Mon, 22 Mar 2010 10:41:13 +0100 |

Dear b, Though I am not sure if I am reading your data correctly (due to plain text format), I would suggest an OLS with clustered standard error: ................begin example................................... set obs 12 input concentration sample condition time id .2 1 1 0 1 .3 1 1 1 2 .3 1 1 2 3 .2 2 1 0 4 .5 2 1 1 5 .9 2 1 2 6 .7 1 2 0 1 .7 1 2 1 2 .9 1 2 2 3 .7 2 2 0 4 1.02 2 2 1 5 1.03 2 2 2 6 end regress concentration sample condition time, robust cluster(id) Dr. Carlo Lazzaro Studio di economia sanitaria Via Stefanardo da Vimercate, 19 20128 Milano tel/fax: 02 26000516 portatile: 335 6786741 e-mail: carlo.lazzaro@tin.it carlo.lazzaro@tiscalinet.it -----Messaggio originale----- Da: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] Per conto di b. water Inviato: lunedì 22 marzo 2010 3.03 A: statalist@hsphsun2.harvard.edu Oggetto: st: which statistics to use Dear all, Stata 8.2, I have data consisting of serum concentrations measured at regular intervals but under two different conditions (but a few missing reading here and there) like so: condition_1 condition_2 t0 t1 t2 t0 t1 t2 sample_1 0.2 0.3 0.3 0.2 0.5 0.9 sample_2 0.7 0.7 0.9 0.7 1.2 1.3 . . . . . . sample_n 0.3 0.5 0.6 0.3 0.8 1.1 Just 'eye-balling' the data I can see that condition_2 did affect the concentrations. My questions: 1. How may I show that in condition_1 concentration at t1 and t2 _are_ statistically different from t0 (if indeed they are). Had it been just t0 with one other time interval, I would have thought of paired t-test off the bat but don't what to do in this circumstances. It looks like ANOVA but again would appreciate advice. 2. How may I show (statistically that is - and therefore what statistical analyses I should deploy) that w.r.t. t1 and t2 that condition_2 IS different from condition_1. Thank you for advice/help. bw _________________________________________________________________ Hotmail: Trusted email with powerful SPAM protection. http://clk.atdmt.com/GBL/go/210850553/direct/01/ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**RE: st: R: which statistics to use***From:*"b. water" <barleywater@hotmail.com>

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