Summary: Ecological Methods I

Read the summary and the most important questions on Ecological Methods I

• 1 Week 1

• 1.1.2 Tutorial

• What do Std bars in graphs tell us?

  The standard deviations illustrate the mean plus and minus 1 standard deviation, indicating that 68% of the data fall within this interval (see lecture slides of this morning).

• When will Std not change with increasing sample size?

  If your samples are large enough and are drawn randomly.

• What does a 95% confidence intervall tell us?

  How certain you are about the mean.
  

  • Larger N --> more confident about mean,  smaller confidence interval
  • Smaller Std --> more confident about mean,  smaller confidence interval

• What do you show when you want to illustrate a measure of the distribution of your data set?

  The standard deviations. 

• What do you show when you want to illustrate whether one mean is significantly different from another mean?

  The 95% confidence interval or standard error.

• 1.2.1 Lecture

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• What is the basic formula of a hypothesis?

  If..., then..., because....

• What factors determine whether you use a 1- or 2- tailed test?

  • Hypothesis
    
  • Previous knowledge
  • Experimental set-up

• Why is a paired t-test often stronger than an independent t-test?

  Because it takes into account the differences of the individual.

• 1.2.2 Tutorial

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• When then 95% CI is from -0.0559622 to 1.9240378, is p larger or small than 0,05?

  P>0.05.
  

  • It overlaps with zero, since the one end of the interval is positive, and the other is negative
  • We are not (95%) certain that the value is different from 0

• What can a reduction in effect size result from?  

  • the means become closer
  • the standard deviations become larger.