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BM3502 Neuroscience & Neuropharmacology Data Handling Dr Derek Scott

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Why use statistics? When analysing data, you want to make the strongest possible conclusion from limited amounts of data. To do this, you need to overcome 2 problems: Important differences can be obscured by biological variability and experimental error. This makes it difficult to distinguish real differences from random variability. The human brain excels at finding patterns, even from random data. Our natural inclination (especially with our own data) is to conclude that any differences are real, and to minimise the contribution of random variability. Statistical rigor prevents you from making this mistake. I am not a statistician, and I don’t expect you to be either – DON’T PANIC!! You do have to be aware of the more basic ways we analyse data. We cover statistics in 4 th year as well so don’t worry!

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Prism 5 A bit like Excel, but much more powerful. Can rearrange columns to suit different types of data. It automatically plots graphs for you. These look a lot better than those in Excel. Very sophisticated equations allows it to do the messy work of statistics and fitting curves for you without you having to understand it all. Produces statistics for you in seconds.

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Gaussian Distribution “Bell-shaped” curve

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P Values P means probability Just gives you an indication of whether an effect is due to chance or not. P<0.05 mean something is significantly different. All this represents is that there is a less than 5% chance that any effect is due to random chance i.e. you are more than 95% sure that you are seeing a significant effect. Smaller P values mean that you are more sure that there is a significant difference.

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P Values – How do we write them? P ValueWordingSymbol > 0.05Not significantns 0.01 to 0.05Significant* 0.001 to 0.01Very significant** < 0.001 Extremely significant ***

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Compare 2 means and get a P value Is there a significant difference? IRON (100 M)ZINC (100 M) Krebs pH 6.0Krebs pH 7.4

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Doesn’t have to be bar chart 4 o C 37 o C IRONZINC

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Can be more than two means that you compare IRONZINC 8-Br cGMP + Staurosporine Staurosporine (0.5 M) 8-Br cGMP (100 M) Control

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What to do today Log on to a PC. You may work in pairs for this exercise if there are not enough PC’s. Go to the Desktop folder for “Life Sciences & Medicine”, then open “Medical Sciences”, then “Biomedical Sciences”. Open “Prism 5”. DO NOT USE Prism 3 or 4 – you will not all be able to access the program, and the layout is slightly different to the instructions given in this handout. Open the “BM3502” folder within the “Biomedical Sciences” folder, and open the “Stats1.xls” file. This contains the experimental data that you will analyse with Prism.

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Statistics. Hypothesis Testing Hypothesis is a ‘testable statement’ Types = alternate, research, experimental (H1), null (H0) They are 1 or 2 tailed (directional.

Statistics. Hypothesis Testing Hypothesis is a ‘testable statement’ Types = alternate, research, experimental (H1), null (H0) They are 1 or 2 tailed (directional.

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