Answer:
Type I error
Step-by-step explanation:
A type I error occurs if the null hypothesis is rejected when it is actually true.
Type I Type II
Reject null when true Fail to reject null when not true
Null hypothesis: ∪ = 30%
Alternative hypothesis: ∪ > 30%
The researchers concluded that more than 30% of first-grade students at this school have entered the concrete operational stage of development and they rejected the null hypothesis.
However, a census actually found that in the population of all first graders at this school, only 28% have entered the concrete operational stage.
A type I error has been made because in actuality the null hypothesis was true but was rejected.
