Table 1

Methodological characteristics of data-based studies included in review (N=131)

n (%)
 Quantitative107 (81.7)
 Qualitative22 (16.1)
 Mixed methods (quantitative and qualitative)2 (1.5)
 Analysis of text or visual materials9 (6.9)
 Key informants2 (1.5)
 Focus groups6 (4.6)
 Other qualitative design5 (3.8)
 Cross-sectional survey100 (76.3)
 Prospective survey6 (4.6)
 Experimental design1 (0.8)
 Other quantitative design1 (0.8)
Sampling methodology*
 Convenience sample assessed50 (38.2)
 Entire population or a random sample assessed73 (55.7)
 Archival data assessed9 (6.9)
Sampling frame
 Educational institution75 (57.3)
 Café/restaurant8 (6.1)
 Local community, including health clinics19 (14.5)
 National5 (3.8)
 Multiple frames15 (11.5)
 Archival data9 (6.9)
Representativeness of human samples (n=111)
 Not representative47 (35.9)
 Representative of the population of a city, state or region10 (7.6)
 Representative of the population of a nation4 (3.1)
 Representative of a school system or educational institution53 (40.5)
 Representative of waterpipe customers in a retail establishment4 (3.1)
Representative of other populations5 (3.8)
  • *Numbers total >131 due to some studies having multiple samples and/or frames.