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Statistics course and homework discussion. Elementary statistics.enWed, 01 Mar 2017 20:19:00 GMTvBulletin60http://www.talkstats.com/images/misc/rss.pngStatistics Help @ Talk Stats Forum - Statistics
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Which test to determine if statistically significant
http://www.talkstats.com/showthread.php/68817-Which-test-to-determine-if-statistically-significant?goto=newpost
Tue, 28 Feb 2017 17:42:39 GMTWhat test can I use to determine if a result is statistically significant, see screenshot: https://www.screencast.com/t/y5z9SpFtW. 5% of the orders...What test can I use to determine if a result is statistically significant, see screenshot: https://www.screencast.com/t/y5z9SpFtW. 5% of the orders generate 8% of the revenue for a specific channel, but the order count is small (under 30). I'd like to determine if the channel performance is statistically significant and we should focus more on it. Thanks in advance for helping this newbie (not a statistician, just would like to increase rigor of analysis).
]]>Statisticsjasonwebberhttp://www.talkstats.com/showthread.php/68817-Which-test-to-determine-if-statistically-significantTwo sample t-test for comparing percentage changes in numbers of settlements?
http://www.talkstats.com/showthread.php/68809-Two-sample-t-test-for-comparing-percentage-changes-in-numbers-of-settlements?goto=newpost
Mon, 27 Feb 2017 19:58:58 GMTHello, as a historian with little formal training in statistics (read none) I might be asking a silly question, but from what I’ve researched I think...Hello, as a historian with little formal training in statistics (read none) I might be asking a silly question, but from what I’ve researched I think I may be able to use a t-test for the case below. I just want to see if anyone catches any mistakes or sees any way to refine it.

My data are a collection of archaeological sites from various time periods located within a 5 km radius of another collection of hillforts. I want to compare the rates of change in the number of these surrounding sites from period to period (Roman to late antique to early medieval) with the rate of change in the percentage of hillforts (from the total number I have collected) that have at least one of these surrounding sites in each period. Both of these rates of change are expressed as percentages. So for example, between the Roman and late antique periods there is a 70.2% drop in the number of surrounding sites, but only a 19.7% drop in the number of hillforts with at least one of these sites within 5 km. The gap between these different rates of change seemed important to me since they are related changes so I looked for ways to quantify this. I came across a two sample t-test on percents as a way to compare these two values since they have different sample sizes (in the example above, the number of surrounding sites from the Roman to late antique periods drops from 477 to 142 and the percentage of hillforts with at least one surrounding site drops from 95.3% to 75.6%).

So my main question is whether a two sample t-test can be used to compare these changes in percents. More importantly, what would I use for the sample size? For the example above, would I use 477 as the sample size for the drop in surrounding sites from Roman to late antique periods, and 86 as the sample size for the drop in percentages of hillforts with at least one surrounding site since this is the total number of hillforts I am deriving this percent change from?

Any help or guidance would be really appreciated, thanks!
]]>StatisticsBadlydrawnboy8http://www.talkstats.com/showthread.php/68809-Two-sample-t-test-for-comparing-percentage-changes-in-numbers-of-settlementsA method sensitivity 1:10^3 or 1:10^5
http://www.talkstats.com/showthread.php/68808-A-method-sensitivity-1-10-3-or-1-10-5?goto=newpost
Mon, 27 Feb 2017 16:44:42 GMTI am developing a PCR method to assess A cell contamination in B cells population. A cell express a large amount of C gene, but B cell only express...I am developing a PCR method to assess A cell contamination in B cells population. A cell express a large amount of C gene, but B cell only express very low level of C gene. PCR study shows that I can tell C gene expression increase significantly if there is one or more A cell in 10^3 B cell population in one PCR reaction.
If I run PCR reaction 100 times and it shows no C gene increase in 10^3 B cells, can I say that there is no A cell contamination in 10^5 B cells, based on that I sampled 10^5 B cells.
]]>StatisticsStemhttp://www.talkstats.com/showthread.php/68808-A-method-sensitivity-1-10-3-or-1-10-5