# Stats help A2 isa AQA biology

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#1
Hi, their could you explain to me what you mean by chance.
Chi squared:
- if you reject the null hypothesis what does that mean in terms of chance/ probability (i.e p<0.05 or p>0.05) and what does it mean p mean in context to the question.
How would you know if its above p is above or below 0.05?
-If you accept the null hypothesis what does that mean in terms of chance/probability.
(i.e p<0.05 or p>0.05) and what does it mean p mean in context to the question.
How would you know if its above p is above or below 0.05?

Spearman rank correlation coefficient
- if you reject the null hypothesis what does that mean in terms of chance/ probability (i.e p<0.05 or p>0.05) and what does it mean p mean in context to the question.
How would you know if its above p is above or below 0.05?
-If you accept the null hypothesis what does that mean in terms of chance/probability.
(i.e p<0.05 or p>0.05) and what does it mean p mean in context to the question.
How would you know if its above p is above or below 0.05?

Standard error and 95% confidence limits
- if you reject the null hypothesis what does that mean in terms of chance/ probability (i.e p<0.05 or p>0.05) and what does it mean p mean in context to the question.
How would you know if its above p is above or below 0.05?
-If you accept the null hypothesis what does that mean in terms of chance/probability.
(i.e p<0.05 or p>0.05) and what does it mean p mean in context to the question.
How would you know if its above p is above or below 0.05?﻿
0
6 years ago
#2
(Original post by optic123)
Hi, their could you explain to me what you mean by chance.
Chi squared:
- if you reject the null hypothesis what does that mean in terms of chance/ probability (i.e p<0.05 or p>0.05) and what does it mean p mean in context to the question.
How would you know if its above p is above or below 0.05?
-If you accept the null hypothesis what does that mean in terms of chance/probability.
(i.e p<0.05 or p>0.05) and what does it mean p mean in context to the question.
How would you know if its above p is above or below 0.05?

Spearman rank correlation coefficient
- if you reject the null hypothesis what does that mean in terms of chance/ probability (i.e p<0.05 or p>0.05) and what does it mean p mean in context to the question.
How would you know if its above p is above or below 0.05?
-If you accept the null hypothesis what does that mean in terms of chance/probability.
(i.e p<0.05 or p>0.05) and what does it mean p mean in context to the question.
How would you know if its above p is above or below 0.05?

Standard error and 95% confidence limits
- if you reject the null hypothesis what does that mean in terms of chance/ probability (i.e p<0.05 or p>0.05) and what does it mean p mean in context to the question.
How would you know if its above p is above or below 0.05?
-If you accept the null hypothesis what does that mean in terms of chance/probability.
(i.e p<0.05 or p>0.05) and what does it mean p mean in context to the question.
How would you know if its above p is above or below 0.05?﻿

Standard error
If you calculate standard error for each set of repeats you can plot error bars i.e a bar chart of the means with a line showing where the mean + 2xStandard Error and mean - 2xStandard Error lies. If the error bars overlap, there is a more than 5% probability (p>0.05) that the results are due to chance. Therefore you would accept the null hypothesis (i.e no significant difference in the mean values) . If there is no overlap, there is a less than 5% probability (p<0.05) that the results are due to chance. Therefore you would reject the null hypothesis; there is a significant difference between the mean values.

Spearman's rank
Once you have calculated the Spearman's rank value (using the formula found on the sheet) you can compare this to the provided tables of "critical values". The critical value for your set of data is found for n=the number of pairs of data. In these cases use ALARM (Accept if Less And Reject if More). If your Spearman's rank is less than the critical value there is a more than 5% probability (p>0.05) that the results are due to chance. Therefore you would accept the null hypothesis: there is no correlation. If your values is more than critical value, there is a less than 5% probability (p<0.05) that the results are due to chance. Therefore you would reject the null hypothesis;there is a correlation.

Chi squared follows the same idea as Spearman's rank. Except in this case "degrees of freedom" is your number of results - 1 or "n-1".
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