It's all true, best to prepare for your job interview right down to your attire. Dressing for success will help you feel more confident and at ease if you are dressed appropriately. Here's an example of how an interview went with someone who was not dressed appropriately and that someone was me.
Flashback to a time long ago, it was my first interview with a major corporation for a junior recruiter position. I borrowed a 'suit' for my mom. Now my mom is great, but she worked as a part time taste tester at Nabisco and never worked in the corporate world. These 'suits' were really to go out to charity events and my father’s business functions. My mom is also 5ft and I'm 5'6", the suit was black knit with big gold buttons and fringe, you get the picture.
With my hair in a clip and some old high heels I went to the massive building and opened the doors to an overwhelming marble floor, jade trim and mahogany wood reception area. Feeling inappropriately dressed is an understatement. Interview was mediocre. Nervousness set in and I was focused on the ridiculous outfit I was wearing and found it hard to concentrate or exude confidence. Needless to say, I did not get the job.
Best advice for job seekers is make sure you are completely prepared for the interview. It is definitely not uncommon to ask what is the appropriate attire for the interview. With the combination of preparing your answers for interview questions, have questions prepared for the interviewer and lastly wearing the right attire, will make you exude confidence and lead to a positive outcome.