State the null hypothesis for: An experiment testing whether echinacea decreases the length of colds. A correlational study on the relationship between brain size and intelligence. An investigation of whether a self-proclaimed psychic can predict the outcome of a coin flip. A study comparing a drug with a placebo on the amount of pain relief. (A one-tailed test was used.)

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Confidence Intervals

When we calculate intervals in probability and statistics, it can be simply termed as finding out a confidence interval. The confidence interval is usually calculated from the data set which is observed. The value of the parameter that needs to be calculated is present here only.