![]() ![]() This usually means the line had portions that were too pointy or that it was perhaps a bit too blurry in places for the algorithms underlying the DataThief program to follow it. Now, I don’t know about your computer, but on my computer, DataThief gives me an error message “Trace did not reach end point, too many doubles”. This will make DataThief attempt to trace the line. Now click on the icon just to the left of the line graph at the top middle of the control window (the icon with the * * * in it). To change the color of the trace line, click on Edit->Preferences->General->Trace and chose a nice contrasting color. Now we are ready to trace the line, but first we must make sure that our trace is a different color than the line (the default color of the DataThief trace line is black, which unfortunately is the color of the line we are trying to trace here). Make sure the blue circle with the + is on the line… from the color under that circle DataThief determines the color of the line. Drag the red circle to the end of the line. ![]() Drag the green circle to the beginning of your line, and point its little arm in the direction the line is going. You will notice that a green and red circle appear with a + through them. To do so, first click on the icon at the top middle of the control window that looks like a line graph. We would like to extract the line in the figure. Those three points define the coordinate system of the figure, and now if you move that blue point with the + through it around the figure, it will tell you where it is placed in the coordinate system of the figure. Here is where you enter the x,y coordinates in the coordinate system of the figure for each of the three datum points that you just placed. At the top left hand of the control window you will see Ref 0 in red, Ref 1 in blue, and Ref 2 in green. Drag another one to the upper value on the x axis, and the third one to the upper value on the y axis. Drag one of the circles to the intersection of the x and y axes. You should now see the figure in the DataThief control window, with three colored points (red green and blue) that look like a circle with an X through them (there is another blue point that looks like a circle with a + through it… ignore that one for now). And click on File->Open and from the file browser select the figure file. Then download the jpeg for the figure from the html of the paper (or, alternatively, take a screen shot of the figure in the paper). To extract the data from this graph, first download DataThief to your laptop from the DataThief website. Let’s take an example: in the paper “Comparative estimation of the reproduction number for pandemic influenza from daily case notification data” by Chowell et al, there is a figure (Figure 1) that shows daily case notification data of Spanish Flu hospitalizations in 1918 in San Francisco: If the data is in graphical format, there are free programs, such as DataThief, that can be used to extract the data into a numerical file. One thing to keep in mind is that any data that appears in a journal publication is fair game to use, even if it appears in graphical format only. ![]() And of course statistical models are wholly developed using sources of data.īecoming adept at finding sources of data relevant to a model you are studying is a learned skill, but unfortunately one that isn’t taught in any textbook! Limitations and directions for future research are explored.ĭata extraction software meta-analysis reliability single-subject experimental designs validity.Connecting mathematical models to predicting reality usually involves comparing your model to data, and finding model parameters that make the model most closely match observations in data. In addition, both programs allow for reliable extraction of data between raters and between software programs. Study findings suggest that both GraphClick and DataThief III provide valid methods of data extraction. The purpose of this study was to evaluate and compare the validity and reliability of the results yielded by each of these programs when evaluating the results of multiple research studies on the Good Behavior Game, a classroom-based intervention that has been in practice since 1969. Researchers consistently use two software programs, DataThief III and GraphClick, to conduct meta-analytic work using SSEDs. Until recently, researchers wishing to undertake meta-analytic research themselves have had limited options for synthesizing the intervention effects of a collection of studies. In the realm of single-subject experimental designs (SSEDs), meta-analyses have a particular cachet: retaining the rigor of single-subject designs with the added robustness of replication to more fully determine the strength of a given approach or intervention. Researchers frequently rely on meta-analyses of prior research studies to efficiently evaluate a broad spectrum of results on a particular topic. ![]()
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