Thursday, November 27, 2014

SERVING THE CITY OF ANGELS: How Important is 'Service' among LA Restauranters?

Ahh the City of Angels (LA).  Like the previous post about serving the Big Apple, I will now discuss how important service is to different categories of restaurants in LA.  To address this, I used Yelp comment data (as of Nov 6th, 2014) from the top 40 restaurants from 44 different categories of cuisines.  I looked at high (5-star) and low (1-star) comments in order to discover the relative impact of positive and negative service in restaurant assessments.

To calculate the importance of service, I used a text mining method called term frequency inverse document frequency (tf-idf) (see previous post on serving the Big Apple for details on this method).

Figures 1 and 2 below are some example word clouds that illustrate the relative importance (i.e. relative tf-idf) of the word service.  More specifically, each word cloud below shows the top 50 tf-idf words from positive (Figure 1) and negative (Figure 2) comments in a particular restaurant category, and sizes the words by its relative tf-idf value.

Figure 1
French Restaurant Category Word Cloud (Positive 5-Star Comments)
Relatively High Service Importance

Figure 2
Pizza Restaurant Category Word Cloud (Negative 1-Star Comments)
Relatively Low Service Importance

High Yelp Ratings 

Using only 5-star rated comments from the different categories of restaurants, I found the following (Figure 3) relative tf-idf values for the word service ordered by restaurant category from highest to lowest.

Figure 3

The categories with the most positive service comments were steakFrenchItalian, and diner restaurants.  The restaurant categories with the least positive service comments (note that this does not mean negative, simply less impact of service) were foodstandsfish n chipspizza, and Filipino.  

Low Yelp Ratings 

Using only 1-star rated comments fron m the different categories of restaurants, I found the following (Figure 4) relative tf-idf values for the word service ordered by restaurant category from highest to lowest.

Figure 4

The categories with the most negative service comments were from cafes, Korean, breakfast/brunch, and traditional American restaurants.  The restaurant categories with the least negative service comments were food standspizzafood courts, and fondue.

As was found in the Big Apple, a positive relationship was found between high and low service normalized tf-idf values (p<0.001).  Thus, the more importance LA restaurant diners placed on positive service, the more they placed on negative service as well (and vice versa).  Next I examined whether the price of the restaurant influenced how important service was for the diners.  To examine this possibility, I used Yelp's restaurant pricing system ($, $$, $$$, $$$$).  These dollar signs represent the cost per person for a meal including one drink, tax, and tip (see Serving the Big Apple post for details).

For each category of food, I calculated a PRICE SCORE to quantify the overall price of a particular restaurant category from its top 40 restaurants using the following equation:

(# of $ restaurants) + 2*(# of $$ restaurants) + 3*(# of $$$ restaurants) + 4*(# of $$$$ restaurants)

As opposed to the Big Apple, I found a marginally insignificant (p=0.051) positive correlation between price score and positive service importance (from 5-star Yelp comments).  Although a negative correlation was found between price score and negative service importance (from 1-star Yelp comments), this correlation was not significant (p=0.658).

I deduce two salient possibilities from this data:

1.  The price of LA restaurants do not necessarily equate to better service. 
2.  LA restaurant diners may generally place more importance on other factors (e.g. ambience, taste, plating).

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