A team of marine biologists investigated the impact of microplastic concentration on the physical performance of zebrafish (Danio rerio).

A matched-pairs design was used, consisting of 12 pairs of genetically identical sibling zebrafish. For each pair:

Environment A: One sibling was exposed to a low microplastic concentration (0.01 mg/L).
Environment B: The other sibling was exposed to a high microplastic concentration (1.0 mg/L).

The biologists recorded two measures for each fish:

the maximum swimming speed achieved during a 5-minute physical challenge, in $cm/s\text{cm/s}$ .
the average frequency of opercular (gill) beats per minute.

The mean results for each measure across the 12 pairs are summarised in Table 1.

Mean scores	Environment A: Low Microplastics	Environment B: High Microplastics
Mean maximum speed ( $cm/s\text{cm/s}$ )	14.8	9.3
Mean gill beat frequency (beats/min)	82.1	114.5

A team of marine biologists investigated the impact of microplastic concentration on the physical performance of zebrafish (Danio rerio).

A matched-pairs design was used, consisting of 12 pairs of genetically identical sibling zebrafish. For each pair:

Environment A: One sibling was exposed to a low microplastic concentration (0.01 mg/L).
Environment B: The other sibling was exposed to a high microplastic concentration (1.0 mg/L).

The biologists recorded two measures for each fish:

the maximum swimming speed achieved during a 5-minute physical challenge, in $cm/s\text{cm/s}$ .
the average frequency of opercular (gill) beats per minute.

The mean results for each measure across the 12 pairs are summarised in Table 1.

Mean scores	Environment A: Low Microplastics	Environment B: High Microplastics
Mean maximum speed ( $cm/s\text{cm/s}$ )	14.8	9.3
Mean gill beat frequency (beats/min)	82.1	114.5

Inferential testing (A-level only)

Inferential testing (A-level only) Questions