# O cockle, where art thou?

## Austina Clark

This lesson investigates the growth of a shell fish in relation to the location or distance from sea water using data collected in a sandy, tidal inlet.

### Video

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There are two data files associated with this presentation: These two Excel files have the data for the 63 quadrats measured in this experimental study. The six variables are defined in the second file.
• Task 1: Draw the box-whisker plots for biomass by area for the three locations F (Furthest), M (Middle) and N (Near). Also draw the histograms for the three areas. Set up confidence intervals for the three mean biomass levels.
• Task 2: Draw box-whisker plots for the cockle densities per quadrat for the thrww areas and construct the confidence intervals for these mean densities at F, M and N. Report conclusions.
• Task 3: Carry out a one factor analysis of variance with biomass as response and area as the factor. Carry out one independent samples test for one pair of the means.
• Task 4: Carry out a two factor analysis of variance with the two factors group and area. Include the interaction between these two factors. Obtain the plot of means and the residual plot.
• Task 5: Draw the scatterplot between biomass and density. Interpret the plot and then fit a linear regression with biomass as response.
• Task 6: Add water level as a predictor and also the interaction between density and water level to the model, using the Undergraduate version to carry out this multiple regression.
If you have access to GenStat, you can go through the lesson Cockles-GenStat.pdf.

Video content recorded and edited by Robert van der Vyver[1] and John Harraway[2].
Web site developed and maintained by Greg Trounson[2] and John Harraway[2]