Maths Skills
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What can we calculate to decide if our data is reliable?
Standard deviation
What does a high standard deviation tell you about your data?
The data varies a lot from the mean, therefore it is not reliable data.
What does a low standard deviation tell you about your data?
The data doesn’t vary a lot from the mean, therefore it is reliable data.
You have collected data on the number of moths collected in 2 locations. You plot your data and add error bars using standard deviation data. The error bars overlap, what does this tell you about your data?
There is not a significant difference between the number of moths collected in each location.
You calculate that the standard deviation of some data you have collected is 0. What does this tell you about your data?
That all of the data is the same. Therefore there is no variation from the mean.
You are investigating to find out if there is a significant difference between the median number of snails in a grassland and woodland. Explain which statistical test you would use.
Mann Whitney U As you want to find out if there is a significant difference between 2 medians. And you have count data.
You are investigating to find out if there is a significant correlation between test score in Chemistry and Maths. Explain which statistical test you would use.
Spearman’s rank As you want to determine if there is a significant correlation.
You are investigating to find out if there is a significant difference between actual the number of moths found in an area and the expected number of moths in the area. Explain which statistical test you would use.
Chi squared As you want to determine if there is significant different between observed and expected values.
You are investigating to find out if there is a significant difference between the mean height of two groups of crops which were given different fertilisers. Explain which statistical test you would use.
T-test As you want to determine if there is a significant difference between 2 means. And you have measurement data.
You are investigating to find out if there is a significant relationship between the amount of rainfall in a year and the amount of crop produced. Explain which statistical test you would use.
Spearman’s rank As you want to determine if there is a significant correlation.
You are investigating to find out if there is a significant difference between the median number of caterpillars on a tree in the shade compared to a tree in the sunlight. Explain which statistical test you would use.
Mann Whitney U As you want to find out if there is a significant difference between 2 medians. And you have count data.
You are investigating to find out if there is a significant difference between the mean air pollution levels in the city centre and the countryside. Explain which statistical test you would use.
T-test As you want to determine if there is a significant difference between 2 means. And you have measurement data.
You are investigating to find out if there is a significant difference between actual the number of seeds that germinated and expected number of seeds that germinated. Explain which statistical test you would use.
Chi squared As you want to determine if there is significant different between observed and expected values.
What type of data is needed for a t-test?
Measurement data
What type of data is needed for a Mann Whitney U test?
Frequency data
What is a general null hypothesis for a chi squared statistical test?
There is no significant difference between the observed and expected values.
What is a general null hypothesis for a spearman’s rank correlation coefficient test?
There is no significant correlation between the 2 sets of data.
What is a general null hypothesis for a t-test?
There is no significant difference between 2 means.
What is a general null hypothesis for a Mann Whitney U test?
There is no significant difference between the 2 medians.
In a chi-squared test, when is your data significant?
When the chi squared value is larger than the critical value.
In a spearman’s rank correlation coefficient test, when is your data significant?
When the correlation coefficient is larger than the critical value.
In a t test, when is your data significant?
When the t value is larger than the critical value.
In a Mann Whitney U test, when is your data significant?
When the smaller U value is smaller than the critical value.
What p value in a critical value table do we normally use?
0.05