5B.6-7 (eco stats) y13

You record % cover of grass in quadrats and soil nitrate concentration. Which test is most suitable?

• • t-test

• Spearman’s rank

• Chi-squared

• • ANOVA

You record the presence or absence of earthworms in grass vs. bare soil. Which test is most suitable?

• • t-test

• Spearman’s rank

• Chi-squared

• • ANOVA

Which test would you use to see if plant species richness is linked to soil moisture?

• • t-test

• Spearman’s rank

• Chi-squared

• • ANOVA

(Short answer question)
You want to see if the mean number of daisies differs between trampled vs. untrampled grass. Which test would you apply and why?

An rₛ of –0.85 indicates:

• • Strong positive correlation

• Weak negative correlation

• • Strong negative correlation

• No correlation

• Which of these is an assumption of Spearman’s rank test?

• Data are categorical

• Means of two groups are compared

• Data follow normal distribution

• Data are categorical

(Data table + Numeric entry): Plant heights (cm) in two habitats:

• Habitat A: 10, 11, 9, 12, 10

• Habitat B: 13, 15, 14, 16, 14

Perform a t-test. Enter your t-value.

What does it mean if your calculated t-value is smaller than the critical value?

Why should sample sizes be similar in both groups when using a t-test?

• To reduce bias and improve validity of comparison

• To increase correlation

• To simplify ranking

• Because chi-squared requires it
  

(Short answer question)
If χ² calculated = 2.0 and critical value = 3.84, what do you conclude?