Table 2Scoring algorithm for quality rating

Definition and Scoring AlgorithmRating
Score Algorithm for Internal Validity Quality Rating
• No negative scores, lowest loss-to-followup score, and lowest dropout rateGood internal validity
• One to three negative scores or intermediate loss-to-followup score or dropout rateFair internal validity
• High loss-to-followup score or high dropout rate ORPoor internal validity
• Four negative scores OR
• Three negative scores and intermediate loss-to-followup score
Score Algorithm for External Validity Quality Rating
• No negative scoresGood external validity
• One to three negative scoresFair external validity
• Four or more negative scoresPoor external validity
Score Algorithm for Overall Quality Rating
• Good internal validity and good external validityGood overall
• Fair internal validity and fair external validity ORFair overall
• Good internal validity and fair external validity OR
• Good internal validity and poor external validity OR
• Fair internal validity and good external validity OR
• Poor internal validity and good external validity
• Poor internal validity and poor external validity ORPoor overall
• Fair internal validity and poor external validity OR
• Poor internal validity and fair external validity

From: Methods

Cover of Progestogens for Prevention of Preterm Birth
Progestogens for Prevention of Preterm Birth [Internet].
Comparative Effectiveness Reviews, No. 74.
Likis FE, Andrews JC, Woodworth AL, et al.

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