Confidence interval = Point estimate +- t-critical * std errorWhile calculating this confidence interval is it assumed that we are using 2 tailed t test?So if we are given 5% significance level should it be taken as 5% in both tails?

yes we assume a 2 tailed t test. however you may have misunderstood something here.so in a normal distribution for example, if it is a 95% confidence interval (i.e. 5% significance level), it means it is the z-score that leaves a probability of 2.5% (α/2) on the upper tail (right-hand tail) of the standard normal distribution. it isn't 5% in each tail, but 5% in total, which means 2.5% in each tail.so that means t=1.960hope this clarifies

A CFA Level 2 Discussion About Calculating Confidence Interval

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- rahul12
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  24 Feb 2021 at 9:46 am
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  yes we assume a 2 tailed t test. however you may have misunderstood something here.
  
  so in a normal distribution for example, if it is a 95% confidence interval (i.e. 5% significance level), it means it is the z-score that leaves a probability of 2.5% (α/2) on the upper tail (right-hand tail) of the standard normal distribution. it isn’t 5% in each tail, but 5% in total, which means 2.5% in each tail.
  
  so that means t=1.960
  
  hope this clarifies
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