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36
12×3.
Class 7 · Bangla Version · General science
Scientific investigation and evidence
Plan random allocation, repeated measures and a fair comparison.
Original Kidemy further-topic investigation. This optional lesson is shared by related upper pathways; select suitable depth with a teacher. It does not certify complete grade or board coverage.
Learn the idea
Random allocation assigns available items to conditions without deliberately placing the strongest in one group. Repeated measurements reveal variation, but many repeats of one item do not create many independent items. Record exclusions with reasons.
Worked example
Twelve paper helicopters are assigned randomly to two blade designs. Each is dropped three times from the same low height. There are 12 helicopters and 36 drops; these are different counts with different meanings.
- Identify the experimental item.
- Separate item count from repeated readings.
- State limitations and an exclusion rule.
Your written practice
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6
12/2.
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design group
Group assignment precedes measuring outcomes.
Write in your own words. A guardian or teacher should review this response.
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Three drops share the same helicopter’s construction, so those observations are linked.
Explain the repeated-item relationship.
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Record the incident and apply a pre-stated repeat/exclusion rule consistently.
Do not silently discard an inconvenient result.
Apply the idea
Create a safe paper investigation plan with allocation and repeat rules.
Review with a guardian or teacher
- Use the stated evidence or givens.
- Show reasoning rather than only a result.
- Review and explain one correction.
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