We are being asked to find the confidence interval of our estimate

proportion who wore sneakers = 0.3 or 30% =300/1000

95% Confidence limits for proportions=
p= 30%
q=1-p= 70%
n=sample size= 1000
sp=standard error of proportion=square root of (pq/n)= 1.45% =square root of ( 30.% * 70.% / 1000)
Confidence level= 95%
Significance level=alpha (a) = 5% =100% -95%
No of tails= 2
This is 2 tailed because we are calculating upper and lower confidence level

Since sample size= 1000 >= 30 use normal distribution
Z at the 0.05 level of significance 2 tailed test = 1.96

Upper confidence limit= p+z*sp= 32.84% =30.%+1.96*1.45%
Lower confidence limit= p-z*sp= 27.16% =30.%-1.96*1.45%

95% Confidence limit:
Upper limit= 32.84%
Lower limit= 27.16%

Therefore our estimate of proportion that wears sneakers is between 27.16% and 32.84%
or we can say that it is 30% plus/minus 2.84%