Skip to contents

Separate analysis for continuous data

Source: R/sepmodel_cont.R
sepmodel_cont.Rd

This function performs separate analysis (only taking into account concurrent controls) using a linear model.

Usage

sepmodel_cont(data, arm, alpha = 0.025, check = TRUE, ...)

Arguments

data

Data frame trial data, e.g. result from the datasim_cont() function. Must contain columns named 'treatment', 'response' and 'period'.

arm

Integer. Index of the treatment arm under study to perform inference on (vector of length 1). This arm is compared to the control group.

alpha

Double. Significance level (one-sided). Default=0.025.

check

Logical. Indicates whether the input parameters should be checked by the function. Default=TRUE, unless the function is called by a simulation function, where the default is FALSE.

...

Further arguments passed by wrapper functions when running simulations.

Value

List containing the following elements regarding the results of comparing arm to control:

  • p-val - p-value (one-sided)

  • treat_effect - estimated treatment effect in terms of the difference in means

  • lower_ci - lower limit of the (1-2*alpha)*100% confidence interval

  • upper_ci - upper limit of the (1-2*alpha)*100% confidence interval

  • reject_h0 - indicator of whether the null hypothesis was rejected or not (p_val < alpha)

  • model - fitted model

Details

The separate analysis takes into account only the data from the evaluated experimental treatment arm and its concurrent controls and uses a linear regression model to evaluate the given treatment arm. Denoting by \(y_j\) the continuous response for patient \(j\), by \(k_j\) the arm patient \(j\) was allocated to, and by \(M\) the treatment arm under evaluation, the regression model is given by:

$$E(y_j) = \eta_0 + \theta_M \cdot I(k_j=M)$$

where \(\eta_0\) is the response in the concurrent controls; \(\theta_M\) represents the treatment effect of treatment \(M\) as compared to control.

Author

Pavla Krotka

Examples


trial_data <- datasim_cont(num_arms = 3, n_arm = 100, d = c(0, 100, 250),
theta = rep(0.25, 3), lambda = rep(0.15, 4), sigma = 1, trend = "linear")

sepmodel_cont(data = trial_data, arm = 3)
#> $p_val
#> [1] 0.1781052
#> 
#> $treat_effect
#> [1] 0.1344738
#> 
#> $lower_ci
#> [1] -0.1522831
#> 
#> $upper_ci
#> [1] 0.4212306
#> 
#> $reject_h0
#> [1] FALSE
#> 
#> $model
#> 
#> Call:
#> lm(formula = response ~ as.factor(treatment), data = data_new)
#> 
#> Coefficients:
#>           (Intercept)  as.factor(treatment)3  
#>                0.1586                 0.1345  
#> 
#>