Question 22M.2.HL.TZ2.3d
| Date | May 2022 | Marks available | [Maximum mark: 1] | Reference code | 22M.2.HL.TZ2.3d |
| Level | HL | Paper | 2 | Time zone | TZ2 |
| Command term | Explain | Question number | d | Adapted from | N/A |
A group of students used quadrat sampling and the chi-squared test to find out whether the distributions of two plant species were associated with each other or not. These two species were found in the ground vegetation in a woodland ecosystem.
[Source: (left) Pixabay.
(right) Topic, J., n.d. Veronica montana 2. [image online] Available at: http://www.freenatureimages.eu/Plants/
Flora%20S-Z/Veronica%20montana/#Veronica%2520montana%25202%252C%2520Bosereprijs%252C%2520Saxifr
aga-Jasenka%2520Topic.jpg [Accessed 3 December 2019].
The numbers of quadrats with one, both or neither species present were counted and recorded. The observed frequencies from 150 quadrats are shown in the following contingency table.
When the data in the table were used to calculate chi-squared, the calculated value was 0.056. The critical value is 3.84. Explain the conclusion that can be drawn from the calculated and critical values for chi-squared.
[1]
- (when the calculated value is smaller than the critical value) there is no significant association between the two species / H0/null hypothesis accepted;
- it is random chance if both species are either present or absent in most quadrats;
