Figure 1

Comparison of normalisation, standardisation and factor correction. DNA constructs containing different enhancer, promoter, and intron sequences from the rat glutamine synthetase gene coupled to the firefly luciferase reporter gene were transfected into FTO-2B cells. Luciferase activity was measured 64 hours after transfection [1]. This plot shows the activity of 8 different DNA constructs (= conditions) measured in 6 independent measurement sessions (◆ □ ▲ ◇ ●). A: Original measurements, plotted on a logarithmic Y-axis. The approximately parallel lines connecting the results from each session indicate that most of the variation between the sessions is multiplicative. B: Data after normalisation, using condition 1 as 'control' (one session [◆] did not include condition 1 and had to be dropped). Note that the variation in the control condition ('c') is lost. C: Data after standardisation. Note that a linear transformation of the standardised values (standardised* = 410 + 305 × standardised) was required to enable this logarithmic plot. D: Data after applying factor correction. The minimal remaining distance between the lines indicates that factor correction is most effective in removing the multiplicative between-session variation.