On the TWS-3 subtests in the 2006 RCT, Spelling Mastery favored the Predictable Words subtest (effect size 0.57, WWC-adjusted p = 0.07) over the Unpredictable Words subtest (effect size 0.11)¶

Claim · All claims
Evidence · 1 study · causal r2 · q3 · i1 small
Currency · newest study 2014 · not yet checked against its sources · not reviewed by a person

Subclaims¶

q3 i1 In the supplemental findings for Darch et al. (2006), the TWS-3 Predictable Words subtest showed a larger effect (0.57, improvement index +22) than the Unpredictable Words subtest (0.11, +5), and the WWC-computed p-value of 0.07 for the Predictable Words subtest was not statistically significant. → tws3-subtests

Evidence¶

tws3-subtests¶

U.S. Department of Education, Institute of Education Sciences, What Works Clearinghouse. (2014, January). Students with Learning Disabilities intervention report: Spelling Mastery. Retrieved from https://ies.ed.gov/ncee/wwc/InterventionReport/579

q3 · i1 · causal · r2

Supplemental subtest analysis within the Darch et al. (2006) RCT of 42 students. Appendix D prints a TWS-3 Predictable Words mean difference of 3.24 (effect size 0.57, p = 0.04 as reported) and an Unpredictable Words mean difference of 0.71 (effect size 0.11, p = 0.16); after the WWC difference-in-differences adjustment the Predictable Words result was not statistically significant.

"A difference-in-differences adjustment was needed and resulted in a WWC-computed p-value of 0.07 for the TWS Predictable Words subtest; therefore, the WWC does not find the result to be statistically significant."

Discussion¶

Related Claims¶

• Spelling Mastery showed substantively important but not statistically significant positive effects on all four writing measures in a grades 2–4 RCT against basal spelling instruction — related
• Spelling Mastery has potentially positive effects on writing for students with learning disabilities, based on two RCTs with a small extent of evidence — a broader claim this one bears on
• Spelling Mastery produced statistically significant positive effects on all three writing measures in a fourth-grade RCT against Visual Imagery instruction — related