Over the last 130 years, the size of broccoli heads has gotten bigger by almost a gram each year, because breeders have been selecting for larger heads.
Scientific Claim
Head mass in broccoli has increased by approximately 0.89 grams per year since the early 20th century, correlating with the release of newer hybrid cultivars.
Original Statement
“Head mass was positively associated with cultivar release year (p < 0.01) with a slope of +0.89 g year−1.”
Evidence Quality Assessment
Claim Status
appropriately stated
Study Design Support
Design supports claim
Appropriate Language Strength
association
Can only show association/correlation
Assessment Explanation
The study reports a correlation with year of release, not direct causation by breeding. 'Associated' is the correct verb strength for observational data.
Evidence from Studies
Supporting (0)
Contradicting (1)
The study shows that modern broccoli is different from old varieties, but it doesn’t measure how much heavier the heads have gotten each year, so we can’t say if the 0.89 gram increase claim is true.