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Table 3 Methodology characteristics in included ITS

From: Methodology and reporting characteristics of studies using interrupted time series design in healthcare

  N = 116
Description of the analysis 115 (99)
 Segmented regression 90 (78)
 ARIMA model 15 (13)
 Generalised estimating equations 7 (6)
 Change-point analysis 2 (2)
 Mixed model 1 (1)
Autocorrelation was considered 63/115 (55)
Method used to test for autocorrelationa N = 63
 Durbin Watson 22 (35)
 Autocorrelation function 13 (21)
 Partial autocorrelation function 11 (17)
 Ljung-Box 3 (5)
 Examination of residuals 2 (3)
 Portmanteau tests 2 (3)
 Autocorrelation probability 1 (2)
 No test performed 23 (37)
Autocorrelation present if a test was performed N = 40
 No 12 (30)
 Yes 25 (63)
 Not stated 3 (8)
Method used to adjust for autocorrelation N = 48
 Autoregressive error term 14 (29)
 Prais-winsten regression model 8 (17)
 Differencing 3 (6)
 Newey-west standard errors 2 (4)
 Yule-walker regression model 2 (4)
 Did not specify 19 (40)
Order of autocorrelation N = 48
 1 8 (17)
 2 3 (6)
 3 2 (4)
 4 1 (2)
 5 1 (2)
 Did not specify 33 (69)
Nonstationary was considered 9/115 (8)
Method used to test for non-stationary N = 9
 Dicky-Fuller 5 (56)
 ACF and PACF 2 (22)
 Significance testing 1 (11)
 Not stated 1 (11)
Nonstationary was present if a test was performed N = 8
 No 4 (50)
 Yes 3 (38)
 Not stated 1 (13)
Method used to adjust for nonstationary N = 3
 Differencing 2 (67)
 Within the ARIMA model 1 (33)
Seasonality was considered 28/115 (24)
Method used to test for seasonality N = 28
 ACF PACF 5 (18)
 Regression diagnostic tests 1 (4)
 Dicky-Fuller 1 (4)
 Just stated a test was performed 4 (14)
 No formal test 17 (61)
Seasonality present if a test was performed N = 7
 No 6 (86)
 Yes 1 (14)
Method used to adjust for seasonality N = 22
 Covariate 7 (32)
 Seasonal ARIMA 1 (5)
 Differencing 1 (5)
 Not stated 13 (59)
Sample size description N=115
 No 108 (94)
 Yes 7 (6)
  1. Values are n (%). Abbreviations: ARIMA, Autoregressive integrated moving average; GEE generalized estimating equation; ACF, autocorrelation function; PACF Partial autocorrelation function
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