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I have scatterplot in Tableau, and I displayed trendlines. However, I cannot understand why there are three of them.

When I research this on Tableau, they say the upper line is upper 95% confidence, and the lower line is lower than 95% confidence.

When I think of confidence levels, I think if there are 100 black and white marbles and I take a sample and see the ratio, I can say 95% of the time, white marbles will be 40% to 60%

And to create confidence bounds, 92% to 98% of the time, white marbles will be 40% to 60%

But I'm having difficulty translating this to tableau trendlines. Please advise.

enter image description here

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  • Assume your data set as just one random sample drawn from a larger population of possible data sets. You could have sampled another time or place or in a parallel universe.

  • It would have a best-fit trend line also if you could build a scatter plot for the entire population. You can think of your trend line as a sample trend line attempting to estimate this true population trend line.

  • Imagine that you have collected many different sample data sets from that same population and used identical procedures to create scatter plots and trend lines for hundreds or thousands of these data sets which are samples. Now, different samples would lead to different trend lines in each plot.

  • These confidence bands are constructed in such a way that you can expect them to enclose the true population trend line in 95% of your samples.

  • statistical inference is being used to estimate the confidence in the population trend model parameters. All based on the Central Limit Theorem.

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