{"id":10419,"date":"2012-05-16T09:00:31","date_gmt":"2012-05-16T16:00:31","guid":{"rendered":"https:\/\/magoosh.com\/gre\/?p=10419"},"modified":"2016-04-07T16:41:40","modified_gmt":"2016-04-07T23:41:40","slug":"standard-deviation-on-the-new-gre","status":"publish","type":"post","link":"https:\/\/magoosh.com\/gre\/standard-deviation-on-the-new-gre\/","title":{"rendered":"Standard Deviation on the New GRE"},"content":{"rendered":"

Many quake in their boots when they hear that there will be Statistics covered on the GRE. They run to their college stats textbooks, dust off the cover, roll up their sleeves, and start computing the standard deviations of a list of twenty, three-digit numbers. Stop, if this in anyway describes you.<\/p>\n

The Statistics on the GRE is much simpler, and does not test your aptitude at crunching numbers as much as it does your ability to think about Statistics. That is you will rely more on intuition than computation on statistics questions on the GRE. You shouldn’t be so worried about how many statistics questions there are on the GRE<\/a>, anyway.<\/p>\n

To illustrate take a look at the following question.<\/p>\n

1- The standard deviation on a test was 12 points, and the mean was 70. If the scores fell along a normal distribution and student X scored 95 points, then student X scored higher than approximately what percent of students?<\/p>\n

    \n
  1. 2%<\/li>\n
  2. 13%<\/li>\n
  3. 48%<\/li>\n
  4. 96%<\/li>\n
  5. 98%<\/li>\n<\/ol>\n<\/blockquote>\n

    Answering this question correctly requires understanding standard distribution<\/a> (that refers to the distribution of scores along the familiar bell-curve). To understand how standard deviation relates to the bell-curve take a look below:<\/p>\n

    Within 1 Standard Deviation Above the Mean<\/span>= 34%
    \nWithin 1 Standard Deviation Below the Mean<\/span>= 34%<\/p>\n

    Between 1 and 2 Standard Deviations Above the Mean\u00a0<\/span>= 13.5%
    \nBetween 1 and 2 Standard Deviations Below the Mean<\/span>= 13.5%<\/p>\n

    Between 2 and 3 Standard Deviations Above the Mean<\/span>\u00a0= 2%
    \nBetween 2 and 3 Standard Deviations Below the Mean<\/span>= 2%<\/p>\n

    In the problem above, 34% of students scored between 70 and 82. Likewise, 34% of students scored between 58 and 70. This symmetry is very important, and you will notice that the bell curve is symmetrical (or even) on both sides. So, given a large enough sample size, the number of students who scored three standard deviations below the average of 70 (34) is the same as the number who scored three standard deviations above the average (106).<\/p>\n

    Returning to the actual question, we want to find how many standard deviations above the average a score 95 of points is: 95 \u2013 70 = 25, which is a tiny bit more than two standard deviations. The question is asking for an approximation, so we can round down 25 to 24.<\/p>\n

    Looking at table above, we can see that two standard deviations above the norm is better than 34% + 13.5%. The trick here is to not forget to account for the left side of the bell-curve, which is 50% (after all, half the score are on the left side and the other half on the right side\u2014don\u2019t forget the symmetry of the bell-curve).<\/p>\n

    That gives us a total of 50% + 47.5 = 97.5, which approximates to (E) 98%.<\/p>\n

    Let\u2019s try another problem.<\/p>\n

    2. The reaction time of 1000 Rhesus monkeys was measured. The average time it took the monkeys to respond to a quickly moving object in their visual fields was .135 seconds, with a standard deviation of .021 seconds (assume a normal distribution). If one of the geriatric monkeys had a reaction time of\u00a0 .205 seconds, then that monkey\u2019s reaction time is how many standard deviations from the mean?<\/p>\n

      \n
    1. 0 – 1 standard deviations<\/li>\n
    2. 1 \u2013 2 standard deviations<\/li>\n
    3. 2 \u2013 3 standard deviations<\/li>\n
    4. 3 \u2013 4 standard deviations<\/li>\n
    5. 4 \u2013 5 standard deviations<\/li>\n<\/ol>\n<\/blockquote>\n

      This is exactly the sort of daunting problem that the GRE likes to throw at you. Believe it or not, there is very little math involved. Again, you want to rely on intuition more than math.<\/p>\n

      .205 – .135 = .07. If the standard deviation is .021, we can determine the number of standard deviations the monkey\u2019s reaction time is from the mean: .07\/.021, which equals approximately 3.4. Therefore (D) – \u00a0the geriatric monkey\u2019s reaction time is 3 \u2013 4 standard deviations from the mean.<\/p>\n

       <\/p>\n

      Takeaway<\/h2>\n

      To do well on statistics questions on the GRE, you have to rely more on intuition than on number crunching. Having a strong sense of standard distribution and how standard deviation relates to standard distribution will help you immeasurably.<\/p>\n","protected":false},"excerpt":{"rendered":"

      Many quake in their boots when they hear that there will be Statistics covered on the GRE. They run to their college stats textbooks, dust off the cover, roll up their sleeves, and start computing the standard deviations of a list of twenty, three-digit numbers. Stop, if this in anyway describes you. The Statistics on […]<\/p>\n","protected":false},"author":10,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[39,25],"tags":[],"ppma_author":[12264],"class_list":["post-10419","post","type-post","status-publish","format-standard","hentry","category-data-analysis","category-math"],"acf":[],"yoast_head":"\nStandard Deviation on the New GRE - Magoosh Blog \u2014 GRE\u00ae Test<\/title>\n<meta name=\"description\" content=\"Here\u2019s everything you need to know about the Statistics questions on the New GRE, and why you should use your intuition when approaching them.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/magoosh.com\/gre\/standard-deviation-on-the-new-gre\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Standard Deviation on the New GRE\" \/>\n<meta property=\"og:description\" content=\"Here\u2019s everything you need to know about the Statistics questions on the New GRE, and why you should use your intuition when approaching them.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/magoosh.com\/gre\/standard-deviation-on-the-new-gre\/\" \/>\n<meta property=\"og:site_name\" content=\"Magoosh Blog \u2014 GRE\u00ae Test\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/Magoosh\/\" \/>\n<meta property=\"article:author\" content=\"https:\/\/www.facebook.com\/ChrisLeleMagoosh1\/\" \/>\n<meta property=\"article:published_time\" content=\"2012-05-16T16:00:31+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2016-04-07T23:41:40+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/magoosh.com\/gre\/files\/2016\/09\/Magoosh-Facebook-Default-Pic.png\" \/>\n\t<meta property=\"og:image:width\" content=\"1200\" \/>\n\t<meta property=\"og:image:height\" content=\"628\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/png\" \/>\n<meta name=\"author\" content=\"Chris Lele\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:creator\" content=\"@chrismagoosh\" \/>\n<meta name=\"twitter:site\" content=\"@MagooshGRE\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Chris Lele\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"3 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\/\/magoosh.com\/gre\/standard-deviation-on-the-new-gre\/#article\",\"isPartOf\":{\"@id\":\"https:\/\/magoosh.com\/gre\/standard-deviation-on-the-new-gre\/\"},\"author\":{\"name\":\"Chris Lele\",\"@id\":\"https:\/\/magoosh.com\/gre\/#\/schema\/person\/3b6630b4f786513b81a860849cffd546\"},\"headline\":\"Standard Deviation on the New GRE\",\"datePublished\":\"2012-05-16T16:00:31+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\/\/magoosh.com\/gre\/standard-deviation-on-the-new-gre\/\"},\"wordCount\":619,\"commentCount\":33,\"publisher\":{\"@id\":\"https:\/\/magoosh.com\/gre\/#organization\"},\"articleSection\":[\"GRE Data Analysis\",\"GRE Math\"],\"inLanguage\":\"en-US\"},{\"@type\":\"WebPage\",\"@id\":\"https:\/\/magoosh.com\/gre\/standard-deviation-on-the-new-gre\/\",\"url\":\"https:\/\/magoosh.com\/gre\/standard-deviation-on-the-new-gre\/\",\"name\":\"Standard Deviation on the New GRE - 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He's been quoted as a subject expert in many publications, including US News, GMAC, and Business Because.","sameAs":["https:\/\/www.facebook.com\/ChrisLeleMagoosh1\/","ttps:\/\/www.linkedin.com\/in\/chris-lele-095005a0","https:\/\/twitter.com\/chrismagoosh","https:\/\/www.youtube.com\/channel\/UCZ4sGYJ6l0cgnVNIHY8GY6w"],"knowsAbout":["GRE","GMAT","SAT","ACT","MCAT (CARS)","LSAT"],"jobTitle":"Principal Curriculum Manager","worksFor":"Magoosh","url":"https:\/\/magoosh.com\/gre\/author\/chris\/"}]}},"authors":[{"term_id":12264,"user_id":10,"is_guest":0,"slug":"chris","display_name":"Chris Lele","avatar_url":"https:\/\/secure.gravatar.com\/avatar\/39381a6b4ab74cd4c87c7e678683c33c3b18f1e14f6f0ac762a946185968952b?s=96&d=mm&r=g","user_url":"","last_name":"Lele","first_name":"Chris","description":"Chris graduated from UCLA with a BA in Psychology and has 20 years of experience in the test prep industry. He's been quoted as a subject expert in many publications, including<a href=\"https:\/\/www.usnews.com\/education\/best-colleges\/slideshows\/10-test-prep-tips-for-sat-and-act-takers\" rel=\"noopener noreferrer\"> US News<\/a>,<a href=\"https:\/\/www.mba.com\/exams-and-exam-prep\/gmat-exam\/why-take-the-gmat-in-2021-when-many-schools-are-test-optional\" rel=\"noopener noreferrer\"> GMAC<\/a>, and<a href=\"https:\/\/www.businessbecause.com\/news\/gmat\/3263\/mba-admissions-gre-challenges-gmat\" rel=\"noopener noreferrer\"> Business Because<\/a>.\r\n"}],"_links":{"self":[{"href":"https:\/\/magoosh.com\/gre\/wp-json\/wp\/v2\/posts\/10419","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/magoosh.com\/gre\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/magoosh.com\/gre\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/magoosh.com\/gre\/wp-json\/wp\/v2\/users\/10"}],"replies":[{"embeddable":true,"href":"https:\/\/magoosh.com\/gre\/wp-json\/wp\/v2\/comments?post=10419"}],"version-history":[{"count":0,"href":"https:\/\/magoosh.com\/gre\/wp-json\/wp\/v2\/posts\/10419\/revisions"}],"wp:attachment":[{"href":"https:\/\/magoosh.com\/gre\/wp-json\/wp\/v2\/media?parent=10419"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/magoosh.com\/gre\/wp-json\/wp\/v2\/categories?post=10419"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/magoosh.com\/gre\/wp-json\/wp\/v2\/tags?post=10419"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/magoosh.com\/gre\/wp-json\/wp\/v2\/ppma_author?post=10419"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}