Could someone please explain

whyzero being inside or outside the confidence interval tells you whether or not the difference is significant?

**Answer**

If the confidence interval (with your chosen level of confidence) includes 0, that implies you think 0 is a reasonable possibility for the true value of the difference. In general, by ‘significant’ people usually mean that they no longer believe the null hypothesis (0) is a reasonable possibility. Note that if a 95% CI doesn’t include 0, the p-value would be <.05, which is the conventional cutoff for 'significance'.

**Attribution***Source : Link , Question Author : Sara , Answer Author : gung - Reinstate Monica*