To Understand (or Teach) CIs, Adopt an Estimation Mindset

Update 8 June. Some minor tweaks. Addition of the full reference for two papers mentioned.

Of course I would say that, wouldn’t I?! It’s the basis of ITNS and a new-statistics approach. But the latest issue of SERJ adds a little evidence that, maybe, supports my statement above. The article is titled Conceptual Knowledge of Confidence Intervals in Psychology Undergraduate and Graduate Students (Crooks, et al., 2019) and is on open access here.

Reading the paper prompted mixed feelings:

  • I’m totally delighted to see this review and some new empirical work on the vital topic of how students, at least, understand CIs, and how teaching might be improved.
  • Most of the previous research that is discussed is quite old, much of it 10 years or more, so dating from well before Open Science and the latest moves to ditch statistical significance. We need more research on statistical cognition and we need it now! Especially on estimation and CIs!
  • Many of the papers from my research group are mentioned, but one fairly recent one was missed. Read about that one here (Kalinowski et al., 2018).
  • The reported study is welcome, but the authors acknowledge that it is small (N=21 undergraduates, 19 graduate students). The undergrads had all experienced the same statistics course, and the grad students ditto.
  • Therefore any conclusion can be only tentative. The authors concluded that, alas, general understanding of CIs was mediocre. In most respects, grad students did a bit better than undergrads (Phew!). Mentioning estimation tended to go with better appreciation of CIs; there was a hint that, perhaps, mentioning NHST went with less good understanding of CIs. But, as I mentioned, the samples were small and hardly representative.
  • The authors suggest, therefore, that teaching CIs along with an estimation approach is likely to be more successful than via NHST. I totally agree, even if only a little extra evidence is reported in this paper.

I’m delighted there are researchers studying CIs, estimation, teaching, and understanding. We do so need more and better evidence in this space. I look forward to some future version of ITNS being more strongly and completely evidence-based than we have been able to make the first ITNS. I’m confident that our approach will be strongly supported, no doubt with refinements and improvements. Bring that on! Meanwhile, enjoy using ITNS.


Crooks, N. M., Bartel, A. N., & Alibali, M. W. (2019). Conceptual knowledge of confidence intervals in psychology undergraduate and graduate students. Statistics Education Research Journal, 18, 46-62.

Kalinowski, P., Lai, J., & Cumming, G. (2018). A cross-sectional analysis of students’ intuitions when interpreting CIs. Frontiers in Psychology, 16 February. doi: 10.3389/fpsyg.2018.00112

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