Correction to: BMC Public Health 20, 805 (2020)
https://doi.org/10.1186/s12889-020-08566-z
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It was highlighted that in the PDF version of the original article [1] an equation was missing under the Sample size section of the Methods. This Correction article shows the correct Sample size section of the Methods. The original article has been updated.
Sample size
Sample size estimation was based on previous study on back care education [14]. Based on this study (pre SD = б1 = 4.82 & post SD = б2 = 4.66) and expecting at least 2-unit difference in mean score of pre and post back care related behavior in intervention group (μ1-μ2); the following formula was used to estimate sample size.
As such a study with 46 participants per group would have 80% power (β = 0.2) at 5% significance level (α = 0.05). However, allowing for a 10% dropout a sample of 52 pupils for each group was thought (in all 104).
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